Easy way by CSV files

Is the data in the CSV file something that you've created by visiting the relevant location and noting the lat and long, or is it some data that's come from someone or somewhere else?

If the latter, then it would make sense to read through one of the many previous questions about importing into OSM (ignore the ones in that list about importing from OSM into a rendering database or Nominatim though). There are a whole bunch of issues you'll need to resolve first. Conveniently, someone has answered exactly that question a couple of hours ago.

If the former, then it's your data, and you can add it. You'll need to make sure that no-one else already has first, though, so it'll still be a manual excercise once you've got the data into a format that you can upload, and you'll still need to check with the local community that they want this data imported.

If you're unfamiliar with how OSM data is structured currently I'd have a read of the beginners' guide, particularly the "JOSM" track of that (since that's what you'll probably end up using to upload the data).

Once you've done that**, you're familiar with mapping, you're familar with JOSM, and everyone's happy with the data being uploaded, if you've still got any questions, come back here and ask!

** you may already have gone through all of these steps already, of course - the problem is that many people don't before asking questions like "how do I upload a CSV?".