Hi there
To apply for a first job, fast food places like McDonalds will just let you apply online through their website, which is useful. If you wanna try something a bit different, you can always apply to places like rebel, a local cafe / small business, etc.
In terms of actually how to apply, when in doubt, just ask! For a lot of places you just wanna walk into the shop and say "Hi! I was wondering if there was someone here that I could hand me resume into? I'm looking for some casual work." They will then direct you to a manager or you can hand a printed resume straight to whoever you are talking to, and often they will pass it onto their hiring manager or whoever is in charge. This is what I did earlier today and I have handed four resumes into local cafes in my area, so it's definitely worth a shot!
In terms of what to put on your resume when you have no experience, make sure to include your name, email, phone number, availability, experience (even if this is your first job, put down things like volunteering, babysitting (even if it was only once - they don't have to know that!), leadership roles within your school, etc), any notable awards or performances, and your referees.
In case you didn't know, referees are people who your potential employer can call up and ask about what you're like, your commitments, etc. I've found that most adults are okay with them being referees - you just have to ask! My referees were my school's deputy principal and my old piano teacher, but really whoever you can get is great!
I found the whole resume and applying process really overwhelming at first, but it ended up being a lot simpler than I thought in the end. I hope this helps, and if you have any more questions just let me know
Good luck!!