Hi, Welcome to the FF.
It's the same as most other car battery fitting except that the positive terminal clamp is part of the small master fuse board.
Loosen the +ve terminal clamp, then remove the 2 screws from the red staple like clip (if fitted) and remove the clip. You can then lift the terminal complete with fuse board away from the battery. When refitting, your new battery may not have holes for the red clip. If that's the case, the clip is not essential so leave it out, but make sure the fuse board it sitting flat on top of the battery before tightening the +ve clamp.
The negative terminal may have 2 or 3 black wires attached to it. Loosen the terminal clamp then lift the terminal complete with wires away from the battery.
Picture below is of a 1.9 Stilo so the battery is larger than in your 1.2. Make sure you get a new battery with the positive and negative terminal posts in the same positions as your current battery.
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