1}Place the headlight into rim
2}fit the top of the "W" into the curled part of the rim.(the part that pushes onto the headlight shell)
3} push the bottom of the "W" onto the headlight edge, making sure it sits in the raised metal holders.
The clips are spring loaded so will bend a certain amount.
This is how i do my T140, i dont know which Triumph you have.
Just remember Gramps!, motorcycles are meant to remind you of your youth, when you last remember being happy, so at least try to relive some of that memory.