won't turn on.

Hi Gay,

The battery is stuck to the inside of the phone with double sided tape. To get to it you have to remove the rear cover of the phone, which is glued on, then unscrew and remove a plastic shield over the motherboard to get to the connector. From there you can unplug it and use the provided tabs to unstick the battery from the phone. iFixit has a step by step guide showing you how to do it.

TCL Stylus Battery Replacement - iFixit Repair Guide

Note that it's not like the old flip phones where you could just open up a sliding cover and pop out the battery; these aren't really made to be replaced by the user, but that's what iFixit is here for; to show you how to do that sort of thing by yourself.