For Friedel-Crafts you need to know:
1) the equation for the formation of the acyl cation
2) the reaction mechanism
3) the equation for the reformation of the catalyst
4) the overall reaction equation and catalyst
Sometimes you will have to do all of it at once, which is in my opinion a relatively simple 4 mark question, and sometimes parts of it are filled in and you might draw an intermediate for example.
I looked for some ppqs on this, 20(a)(iii) on the 2022 paper 2 and 19(b)(iii) on the 2019 paper 2 might be useful to look at (: