Melt the Heat Shrink
Always use a quality dual-wall adhesive lined heat shrink for this part. You’ll want to use a heat gun for the melting as it does a much better job than a flame will.
You want to heat it evenly until adhesive oozes out the ends. Blow up the photo and you can see the adhesive. A dual-wall heat shrink is lined with a heat activated sealant that melts and glues the heat shrink to the wire and terminal as well as seals it.
Once you connect this to the VHF antenna use a self amalgamating tape to seal the entire connector.
There are many methods to install a PL-259. Get on the net, research them and use what you feel comfortable with, you will get many opinions on this. Over the years I have tried most all of the methods and finally settled on this method for many of my PL-259 terminations in the marine environment.My personal preference is still an Amphenol solder/solder PL-259 but this method has proven very reliable.
TIP: When you can, and it works for your boat, try and leave a long enough tail of VHF cable to make it all the way to the VHF radio. This avoids a mast base splice and reduces losses.
When swinging from a bosun’s chair 40-60 + feet up in the air with a 10 knot breeze I can assure you that getting a good solder joint for the braid is nearly impossible, no matter how good you are at soldering. The tip is easy, with a mini butane torch but the shield, not so much, this a crimp solder connector works very well.
Unless you are very skilled at this, which most won’t be, you may ruin a few connectors trying the solder/solder method and may still wind up with a cold solder joint and a failed connection.
The crimp solder method has held up very well for me in the marine environment.
Even with this method I advise buying a couple of extra PL-259’s and practicing first.
Good luck & happy boating!