CFraming welded parts?

I am trying to CFrame two parts on the character to make fake arms but how do I CFrame and rotate without ruining the position?

I am currently doing this is there any better way?

LeftWeld.C0 =,0,0) *, 0, 0)
LeftWeld.C1 = CFrame.Angles(0,0,0) * CFrame.Angles(0 ,0, 0)

why not use motor6d’s,

Can I get an example of what to do in my situation?