You can create a post in your Community in the following steps:
1. Click on the Commerce tab on the left side bar.
2. Click on Community.
3. Click on the Community you want to create a post in.
4. Start a post by clicking on the top space by the + sign and start typing.
5. You can attach a video or a photo.
6. Enter your title and actual post. You can also customize your post.
7. Watch the video below for more information.