Rebuilding fender indicators - gotta cut new wires?

I got a rebuild kit from a Canadian company. It seems to be great quality. Everything was included except the underside brackets which I sourced elsewhere. I went to put the new power wire into the housing only to find... it won’t go in. Both ends are too big for the slot on the bottom. I am guessing this means I need to cut it and install and then solder back? Anyone confirm this?
Being Canadian it is metric. Unless it came from Quebec, then it is French.