This knot works very well and I have never had one let go.
Step 1. double your line to form a loop and pass the doubled line through the eye of the swivel.
Step 2. Pass swivel through the loop and tighten up around eye of swivel to form a half hitch on the swivel.
Step 3. Tie an overhand knot in the main line making sure you have both the main line and the tag end of the loop tied into the overhand knot.
Step 4. Pull tight and trim tag end.
The half hitch on the eye does all of the work, the overhand knot is simply to make sure the wire line doesn't slip through the half hitch.