Well that pic says it all. just need to push out that inner round thing and attach it back to the pin then you can attempt to clip the arm to the strut it belongs to. Clearly the tightening round plastic which should be around the pin went with the strut it's attached to instead of getting left behind with the rest of the arm unit.
Wanted AM partner Vanguard, Myclones Dirge, G1 Victory Leo, e-hobby Dark scream ( the black version), e-hobby Magnificus
Parts- AM partner Basher-side guns, G1 Actionmaster Elite Windmill's blades[I][B]