The single most obvious way to get comfortable is to use it! It's a bit like learning to use chopsticks by picking up shelled peanuts... tricky practice makes perfect. As a point of historical interest, the reason that Microsoft released Solitaire and Minesweeper with Windows was to teach using a mouse. So, you can still find these games, or variants, on pretty much any platform and they're a very good way to exercise your use of any pointing device, including your pen and tablet. I would start there.

Beyond that, there are some basic things you can do...

1. Tweak the active region of the tablet to the area that you can comfortably move your hand to go edge to edge on the screen. When I discovered this tip, it changed my life with a tablet.

2. Spend some time with the general pointer settings in the driver. You need to tweak pointer acceleration, double click speed, etc. and then refine as you get more comfortable.

3. Use it as your mouse, even when not using Photoshop. Goes back to the practice thing.

4. Aaron Nace is your friend. Watch the video, worth your time. You will learn about some of the things I've mentioned and a few more besides. In this episode he covers basic tablet settings, reasons for why, etc.