Just take the fuse holder they send to you. Cut the remnants of the old one off (both ends). Get some heat shrink, correct size, cut it to about an inch or tow ...two pieces. Slip a piece on each of the trailer wire where the fuse holder was. Now crimp the new fuse holder onto the wires, Slip the heat shrink over the splice and heat with a flame.
O.K. The crimp is not tough. Without a hand crimper...lay the wires to be crimped on a hard flat surface with the crimp/splice fitted to the wire ends. Then a punch, small rod or a large flat blade screwdriver (not sharp) smacked sharply on the splice will set the crimp. The wires are set now and should not move.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."