You can do either way. If you give it slowly and let her swallow, no more than .5 ml at a time, you can do in the front of the beak. You don't want to squirt it forcefully or do too much at once that way or she could aspirate it. Or you can do the syringe farther back, to avoid that.
https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/
https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/