Overview: Every Organization, League, Competition and Team has the capability to post to their Feed. Any followers (including team members) able to view Feed posts.
Access Required: League Admins have permissions to add/edit FEED posts (for their Org or Competition). Team Officials all have access to post to their Team.
For Mobile simply go to the entity you wish to post from, then to the Feed tab and you will see a "+" button to add a post:
If you tap on this "+ it will open up for you to put your FEED item.
From the web you can post from your home screen, or from that entities' Feed tab: