If someone posts a picture with you in it on Facebook, you can tag yourself if the photo is configured to allow you to do so. There's no explicit "tag myself" option, but you can click your image in the photo and type in your name or someone else's. If you're tagged in a photo and don't want to be, you can untag yourself.
Tag Yourself in a Photo
If a photo is set up to allow you to tag people in it, you can mouse over a person's image in the photo and type his name in the pop-up box that appears. If you're the person in the photo, type your own name.
If you're tagging someone else's photo, he'll have to approve the tag. If you tag someone other than yourself, that person and his friends will generally be able to see, like and comment on the photo even if they previously could not.
Tagging Someone in a Comment
You can also tag someone in a comment below a photo or another post, which will serve to draw his attention to the post. Usually, Facebook will automatically suggest a friend's name when you begin typing it.
Generally, you wouldn't tag yourself in a comment or post since your name is already associated with it, but you're free to do so if you choose.
Sometimes you may find yourself tagged in a photo or post that you'd rather not be associated with. If this happens, you're free to untag yourself.
Click the downward-facing arrow next to the photo and click "Remove Tag." The photo or post will stay on Facebook, so others may still see it, but your tag will be removed. If you don't want the photo or post on Facebook at all, ask the person who posted it to remove it or make it private. Keep in mind that people may have seen it before you were untagged or before the photo was removed.
If a photo is somehow offensive or violates your rights, you can complain to Facebook and ask that it be taken down. To do so, click on the photo and then choose "Report or Give Feedback."
By default, you must approve it if someone you're not friends with tags you on Facebook, but your friends can freely tag you.
If you'd rather approve tags from friends as well, go to the Facebook "Settings" menu, then click "Timeline and Tagging." Within this setting, click the "Edit" button and choose "Enabled" from the drop-down menu. You will then get notifications to approve whenever you get tagged in a picture.