Is it a Traditions kit?
I could not assemble mine based on what Trinidad College was trying to teach me. I had to use a lot of my knowledge from the NMLRA gunbuilding workshop at Bowling Green, classes at Conner Prairie and a class at the Log Cabin Shop.
Worse thing was having to relieve the bottom of the drum so the barrel/drum would fit the lock. Also had to bend the hammer so it would time with the nipple. Then I also drilled the ramrod hole just so the rod would enter straight.
First thing is to inlet the lock. Where the lock goes determines where the tang and barrel goes.
ETA: OK, found the kit. It's similar and possibly made by the same Spaniards. The grips are different as is the rear sight and the face of the lockplate is plainer (no faux engraving).
https://castboolits.gunloads.com/sho...wken-pistol-50
Watch the video but do not follow those instructions. Post pictures so I can walk you through the assembly. Re: mystery spring. That forward lock screw is pushed partially in and then goes through the spring. The spring provides tension against the ramrod to keep it from falling out.
Especially do not follow his example of loading from the flask. Always use a powder measure. An ember can cause a premature ignition and you don't want to be holding a hand grenade.