Can I use an Apple computer on my Windows network?

Of course you can. I think of Windows and Apple like philips and “flathead” screwdrivers, they are both fantastic tools as long as you understand that they are different. They can work together or individually on the network as long as your IT people know what they are doing.

When is a good time to backup my data?

The best time to run a backup is before you lose data. The second best time would be right now (assuming you haven’t lost data yet).