How do I self host data?

I'm tired of being tied to specific calendars and to-do apps because of difficulties in sharing and syncing my data, so I'd like to be able to manage it myself, either self hosting or using someone else's servers.

I already pay for web-hosting for a personal website (wordpress) but beyond this I'm totally at a loss.

My main goal is incredibly simple - I just want to host some notes and calendars for my family (tomavoid headaches when phones invariably break and so on), which I feel can't be too hard but I'm also incredibly stupid.

Please help?!