Note that you'll need to set up at least one automated feed for this feature to be visible.
When setting up automated feeds you can select if the content is published to section automatically or if you gather the content to the section's inbox for moderation. In addition you can block specific usernames and keywords from Twitter and Instagram feeds. Here's how:
Click 'Automated publishing' on the top navigation after login.
Click 'Blacklist users and keywords' to open the blacklist editor.
Choose Twitter or Instagram.
Write down the usernames and keywords you want to block.
Click the 'Block user' and/or 'Block keyword' buttons to activate.
Now we've got your back and the content is blocked as long as you wish. You can always disable this later. Note that the blacklist will only block future content mentioning the keyword or posted by a user.