TENSED BELT ALTERNATOR OPEL ASTRA 98

Hello everyone, I have changed the alternator of my Opel Astra of 98 (old) and I do not know how the alternator's strap is placed, I have seen that it has a roller that will be the tensioner but I do not know how it moves to tighten the belt, the case is that right now there is the new alternator placed, the belt is in its placed pulleys, but I cannot introduce it in the axis of the alternator, what would you have to do so that it would introduce it to the axis and then tighten it?
I hope you find me, I am a rookie in this.
Thank you

The tensioner support has a wrench and go to a nut

So that you have to weed more, that's all.