BNC connectors are not hard to install, but they must be installed correctly or they can cause problems down the road. I have reproduced below the instructions from Amphenol (the biggest connector maker). I have developed a technique over the years which requires no special tools other than a crimping tool and which I find easier than trying to measure  the dimensions given in the Amphenol instructions below. YOU SHOULD READ THE INSTRUCTIONS FROM AMPHENOL ANYWAY, since some important warnings are contained in them. (Who knows? Maybe you'll find them easier than my technique.)

  My technique:

1) Place the Plug Body assembly on the work surface.
2) Place the male contact pin on the table with the tip of the pin aligned with the front of the plug assembly.
3) Place the cable next to the pin with the end of the cable just beyond the little hole in the side of the pin.
4) Carefully cut the cable outer sheath right where it lines up with the cable-entry edge of the Plug Body.
    Do this with a razor blade or knife being very careful not to nick or cut any of the shield braid wires.
    It's better to remove too little sheath than too much. You can remove more later if necessary.
5) Slide the Outer Ferrule onto the cable.
6) Push back the braid to expose the inner conductor.
7) Using a razor blade or knife, cut off about 4mm (.156") of insulation from the end of the inner conductor.
    Again, be very careful not to nick any of the conductor wires.
7B) If using RG62 cable (93 ohm) put the little bushing onto the center conductor as shown in the picture below. Bushing not needed for RG58.
8) Place the Male Contact Pin onto the inner conductor, making sure all wires are inside the pin. If the pin doesn't fit snugly against the insulation, remove it and trim the conductors until it does. NO INNER CONDUCTOR WIRES SHOULD BE EXPOSED.
9) Using the appropriate crimp tool (the gold-colored one for RG58, found in the "miscellaneous wrenches" drawer in RM 107) crimp the pin onto the inner conductor.
10) Push the Plug Body Assembly onto the cable until you feel it 'snap' into place. The end of the pin should be flush with the edge of the Plug Body. If you can't push it in far enough because not enough outer sheath was removed in step 4, trim a little more of the outer sheath off until the Plug Body goes all the way on and the pin snaps in. BE VERY CAREFUL AT THIS STEP THAT NO BRAID WIRES ENTER THE PLUG BODY. THIS CAN CAUSE A SHORT.
11) Push the braid up over the Plug Body and trim it with a cutter or scissors so that it comes just up to the larger diameter part of the Plug Body. It should come all the way up over the knurled or ridged crimp barrel. Having braid wires stick out because they're too long is unsightly, but a greater problem is having them too short and becoming disconnected from the Plug Body.
12) Slide the Outer Ferrule up over the braid and the plug body as far as it will go, then crimp it in place with the crimp tool.

You're Done!!

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Info from Amphenol:

Stripping Dimension A:.593"(15.1mm)
Stripping Dimension B:.250"(6.4mm)
Stripping Dimension C:.156"(4.0mm)
 

Step 1	Strip cable jacket, braid, and dielectric to dimensions in table above. [for RG-62,71,210/U cable, trim an additional .039"(1.0mm) of insulation off center conductor and add bushing] All cuts are to be sharp and square. Important: Do not nick braid, dielectric, and center conductor. Slide outer ferrule onto cable as shown.
Step 2	Flare slightly end of cable braid as shown to facilitate insertion of inner ferrule. Important: Do not comb out braid. s For RG-174, 179, 187, 188, 316/U cables only, slit jacket back .100"(2.5mm) as shown. Before attaching center contact, slide metal spacer/TFE sleeve (not shown) over cable dielectric and under braid. The center contact should butt against the dielectric and TFE sleeve. s Place contact on cable center conductor so that it butts against cable dielectric. Crimp contact in place using Die Set Cavity indicated in table above. When using RG-62, 71, 210 cable, install bushing over center conductor before installing contact.
Step 3	Install cable assembly into body assembly so that inner ferrule portion slides under braid. Push cable assembly forward until contact snaps into place in insulator. Slide outer ferrule over braid and up against connector body. Crimp outer ferrule using Die Set Cavity specified in table above.