I would recommend you start here - How to fix a hole in a plaster wall. It includes the tools and materials that you will need. If there's a lot of damage to the wall, you might consider replacing it, but I'm sure you will find the repairs are quick and easy.
With older-style plasterboard with hair in it the good news is that the repair job is exactly the same as if you had newer-style Gyprock walls. The Bunnings D.I.Y. Advice How to fix a hole in a plaster wall has step-by-step instructions to follow. - Jason
We hosted an 18th birthday party and there was some over-enthusiastic dancing that meant I had to repair four holes in the wall. I’d never done it before. Patched the holes successfully and they look almost perfect.
I’ve had trouble with a crack. Made a bit of a mess by putting too much filler on, then sanding it back it can still look uneven and messy. But I found it just needed a good sand once it was all nice and dry.
Painted now and all looks good as new. There's just one wall that I reckon could do with another coat. It was an easy DIY job after all.
I can recommend this as very easy to use and got me a perfect finish: https://www.bunnings.com.au/earl-s-multfill-ready-to-use-filler-1kg-white_p1661245 - PartyDad
If you don’t want to buy a whole roll of tape Bunnings do sell Pfeiffer plaster repair wall patches. One for holes up to 10cm, one for 15cm. The process is the same. With bigger holes I would patch the hole behind first by gluing some Gyprock to the back of the hole. Make sure if you do this the edge of your patch Gyprock is recessed to the main wall so you can fill up to the level of the wall. - JDE