How to Install?

I’m new to wordpress and it’s giving me such a headache. I have no idea how to install new themes. I have a free plan and I downloaded this theme onto my computer, but since I don’t have the business plan, I wasn’t able to upload it. I looked up a tutorial and it said to click the add themes button under themes on my site page but there is no such button there. Please help I just want to get rid of the generic theme they start you off with.