Gustavo,
Which spring?
The main spring should come around the cam counter-clockwise (12 o-clock) and attach to a spur at the top of the left side gear train (9 o-clock)
The hair springs for the T&B arms should be self explaining
The second main spring, under the main plate, goes from 9 o-clock to the cocking arm at 12 o-clock.
The self release spring assm goes at 6 o-clock. Tension this 1-1/2 strokes of the self release arm but NO MORE.
I'll see if I still have pix for this,