If you want to go the DIY route, you will have to take your smartphone apart, detaching the screen and other parts before getting to the battery. Since most parts are glued together, you would also have to remove and then reapply adhesive. Do not attempt this if you do not have the right tools. The basic ones you need are a suction handle, flat opening tool, tweezers, heat gun to melt adhesive, and a screwdriver. Replacement adhesive is also a must.
Don’t use just any tools lying around in your house — you can damage your phone.