w do I choose who can see previous posts on my Timeline?
If you want to change who you shared something with after you post it, return to the audience selector and pick a new audience.
Or, if you want to adjust the audience of many posts at once:
Tap (top-left menu) and scroll to the bottom
Tap Account Settings > Privacy
Under the Who can see my stuff? section, tap Limit the audience for posts I've shared with friends of friends or Public?
Tap Limit Old Posts
Some important notes about this tool:
If you want to undo this action in the future, you'll need to adjust the audience of each individual post. Limiting the audience of your previous posts cannot be reversed in one click.
If you have shared a previous post with a Custom audience such as Friends except Acquaintances or Close Friends, this tool will not change the audience for those past posts.
If you tagged someone in the post, the audience of the post will still include the person you tagged and people they include in posts they're tagged in.
This tool only controls the audience for posts you've shared. If you've been tagged in someone else's post, they control the audience for their posts.