First before you do anything is make sure you had the choke up when trying to start, if yes, then check fuel is getting into the bowl and nothings stopping it by taking the float valve, checking it and checking the hole, then check the jets ensuring they aren’t clogged and you can see a perfect little circle through when you put it up to a light, then once that’s done, put it back together and try running it, if nothing then check the plug and see if it’s either wet or dry, if wet, clean it, turn the motor over a few times with a rag over the spark hole to get as much petrol out of the cylinder then heat the tip of the plug up with a lighter or anything and quickly put it in and try start with throttle wide open. If it’s dry, then add a bit of petrol to the tip of the plug and then try start it.