Plug in the charging cable. If you get the charging symbols but cannot turn on the phone, ensure that the side buttons are connected. Peel up the rubber cover plug and push the connector into the receptacle.

If wireless charging is not working, ensure you're trying it with a phone that is fully booted and operational.

If wireless charging is still not working, take it all apart again and carefully transfer the location of the four pins on the phone side to the charging coil connector on the other side.

If the two sides are difficult to close and screw back together, bend the battery so that it is more or less curved - matching the previous battery. There shouldn't be any force necessary to keep the halves closed together.

If the glue on the back cover is weak, try warming the adhesive with a hair dryer before reinstalling. You can purchase replacement covers (with new adhesive) that are rather inexpensive.