If you don’t want to host your own server, but simply want to use your machine as a nextcloud client to an existing (third party) server, all you need to do is:
sudo dnf install nextcloud-client
The client has a simple step-by-step setup guide that will help you connect to a server and setup the shares.
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You didn’t tell us what your desktop environment is, but, for example, in Gnome, you can start Software, search for nextcloud and install the client there.
Another alternative, just to mention it, is installing nextcloud-client from flathub: