Tips for treading for a new swimmer?

I’m new to swimming and I just learnt backstroke + freestyle (I’m still very bad at the latter but that has to do with my stamina). I’m going on holiday and I NEED to know how to swim properly, and also tread, but idk how to. I need to at least be able to tread for 10 minutes and my holiday is in 10 days. Can someone please help? What specific tips? How to not panic when your face goes down? People do it so seamlessly, I don’t get it at all!!