There's no reason for you to have a Target walkie in your possession off the clock, whether it works or not. They're specifically programmed to work with other Target walkies, you do nothing except for turn it on. This would have been covered in your on-boarding/training.
If it doesn't work, give it to a leader or someone knowledgable on the equipment repair process. Get one that works.
If you are trying to figure out how to make a non-Target walkie communicate with the ones that stores use, that's not what this forum is for and you're not going to get answers here.