

You have to host it yourself, pay for it to be hosted for you, or know and trust someone with an instance who is willing to give you an account.
Nextcloud is like Lemmy. Nextcloud is just the software, to use it you need a service provider that’ll give you an actual instance to sign up on. That provider can be anyone, including yourself.
Nextcloud makes free personal accounts available via a couple partners, here: https://nextcloud.com/sign-up/



















I edited my comment.
But if a couple gigs of storage will do, there is this: https://nextcloud.com/sign-up/