A few years ago, after purchasing my actual house (which has a garden with trees), I also was worried about trees and chainsaws.
Now I am quite good at using a chainsaw, and I understand that all my worries were unnecessary. First of all, you need to check if the chainsaw is ready for work, then you need to put some gasoline if it's not full; after that, you turn it on bu pulling the starting cord. Using it is also very easy, and you will get used to it every day more.
You also can check some videos; it can be easier having a graphic representation. And I can also recommend a site which helped me a lot https://bestchainsawadviser.com/jonsered-chainsaw-reviews/. Good luck!