Open Facebook and go to the post you want to make shareable
Click the three dots in the top-right corner of the post
Select Edit audience or Edit privacy
Change the audience to Public
Save the changes
If the post is in a private group or on a restricted profile, change the group or profile privacy settings if needed
Make sure the post does not have sharing disabled by the original creator
For new posts, choose Public before publishing
Check your profile and timeline settings to allow others to share your posts
If sharing is still unavailable, review page or group permissions and restrictions