There are many knots out there for joining braid to a mono/flurocarbon leader. Our favorite in order of performance are:
Click on the links for to see the video on how to tie them.
If you’re running trolling gear, there’s nothing better than using a wind on leader.
For a wind on, you will need to use a Bimini twist to tie a double in your main line and then loop it several times using a cats paw connection to the wind on leader. This is very reliable connection and doesn’t risk undoing itself while trolling like a newly tied FG can do.