Need help with adding a business directory to wordpress site hosted on one.com

So I have agreed to help a family member with their website, which is already created with wordpress (I think, I have a hard time figuring this out) and hosted on one.com (she says she's paid for the hosting but neither of us really understands what is going on). She wants to have a business directory feature where people can search for/order services based on their location. I have been trying to follow instructions from youtube and chatgpt and none of it works. How do I download plugins? It seems like I need

1. hosting services (supposedly already done, one. com)
2. Content management services (also supposedly already done, as I THINK the website is built on wordpress but I can't really tell)
3. change the theme to ListingPro or something else that supports directories??
4. a bunch of plugins like GeoDirectory so people can search for services based on location, but I have no idea how to download these plugins (yourdomain.com/wp-admin just gives me error messages)?

at this point I'm willing to pay someone to do this because it seems so ridiculously complicated and I hate it. I feel terrible that I can't help, but… you know I can't magically do web design just because I'm young ish ;_;