You can edit the community sidebar by clicking on the edit icon above the sidebar.

To remove posts, click on the dots below the title to see your options. It's similar for comments.

To add another mod, find a comment of the user, click the dots to expand possible actions, then click on something like "make mod" or "add as mod".

When users make reports, you'll get a notification on the top right next to your other notifications, but reports have a shield 🛡️ icon instead of a bell.

Sorry I can't be more specific. I'm on Jerboa which doesn't seem to have mod actions.