I really want to get into proofread/ editing. How can I write a cover letter that pertains to that? I don't have any samples or work experience; is there any way I can get these on Upwork from entry-level jobs?
re: "I really want to get into proofread/ editing. How can I write a cover letter that pertains to that?"
I don't know. I have never written a cover letter about what I want.
Every cover letter I write is in response to a specific job posting. I explain how I will do the job for the client. I don't talk about myself. I focus on the client and his project.
Teona, I don't think you fully understand Upwork's purpose. You should probably spend some time reading more about it.
Upwork is not here to help you learn. It is a platform that clients use to hire professionals that can help them with their projects.
I think you will have a better experience if you learn about specific skills that are in demand, gain work experience, and assemble an impressive portfolio demonstrating your skills. You should spend time practicing skills by working for "yourself" as a client. Do projects on your own, for free, in order to master in-demand skills.
Proofreading and editing? Meh. You might be good at doing these things... but is there any money in it for a newbie? Probably not so much. Because there are already so many highly qualified people here offering those skills. If that is really something you want to get into, nobody will stop you, but you should know that there are many skills which are more in demand.