Advice needed about tightening aux belt plz!

[Mister_Lee]

Hiya my aux belt has now squeeking/ slipping. Its a new belt and probably needs some minor adjustment, how do i go about this myself? Had a look at what i believe is the tensioner, its a black circular block with a bolt on one end and a torx bit on the other side between the alternator and block. It seems pretty tight to work on anyone out there got any advice how it tightens and the best tools to do the job please.
Cheers

p.s. If it makes any difference, my cars a clio 1.2 ph1.

 

[JoedotwasT5phy]

just a 17mm (?) socket and a big screwdrive normally does the trick. the bolts that hold the pulleys are on oval bolt holes - one will be in the top of the engine bay, the other you'll have to get at from under the car.