To really get anywhere in knitting, you need to be able to get started. You may well have learnt the knit and purl stitches using some knitting that a kind person had already cast-on for you, otherwise I’m afraid this is where you have to start.
There are a huge number of different methods for casting on - bewildering for the beginner but very useful for a more experienced knitter as they all have slightly different qualities. There are much better tutorials out there on the internet, but I thought I’d round up the methods I use most often.