As the 'community owner' (or moderator), you can delete any message or post that's sent in your home.
On Web / Desktop: To delete a message/post, click on the more option button over the message and select the "Delete" icon
On Mobile: To delete a message/post, click on the more option button over the message and select "Delete"

Note: After deleting a message/post, it's probably a good idea to DM the person who wrote it to let them know that you've removed the content, with a short explanation why.
As the community, you can remove and/or ban people from your community or group at any time. When you remove someone, they can rejoin (or request to rejoin) your community or group. When you ban someone, they won't be able to rejoin (or request to rejoin) unless you unban them. Here's how to remove or ban a member of your home:

If you've changed your mind about a ban and want to allow someone to re-join your community or group, you can unban them. This will not automatically re-add them to the community or group, but will allow them to go through the joining process again.