Gross but Necessary

This might be a gross question but I feel it's a very necessary and legitimate question too. So I am a FTM and will be having my baby in 3 days, so I'm just wondering when it's time for me to push how I do that? What muscles do you use? And how do you know when and at what times to push? Like I said yes I know kinda weird to ask, but I feel like a lot of FTM have the same question. Lol I just want to be prepared and not completely clueless.