This should be a fairly simple process. UV unit manufacturers know you need to change your lamp every year so take measures to make sure it’s as easy as possible to do.
I’ll give a generic description of how to go through the process but feel free to ask me if there’s any make or model you would like to know about specifically.
1. Turn the power off, all of it. I would recommend just unplugging / powering down the unit from the wall.
2. Take your old lamp out. There will be some kind of device supplying the lamp with power, you’ll have to separate it from the UV chamber and / or the UV lamp. Your lamp will slide out once disconnected.
3. Put your new lamp in. Just replace the old once and reconnect. It may be worth just double checking you have the right lamp while you have them both out.
**Optional** Units that have a countdown timer are going to need you to reset the timer at this point. There will be a reset button on the controller if this is the case.
4. Turn the power back on.
5. Have a cup of tea. You deserve it after all that hard work.