How do you write using Graphics Tablet?

Photoshop

First off, you must download the tablet driver onto your computer (that should be included as a CD with your tablet when you buy it). This will help calibrate your tablet to your computer and activate features like pen pressure that could be helpful later on. If the CD is not included with your tablet, drivers can be found on the wacom

website. Make sure you download the correct driver for your tablet.
Then you should get a drawing software like Paint Tool SAI, Photoshop

or if you are unable to acquire those, use the software program that came with your tablet.

It takes time to get used to your tablet. Make sure to practice a lot and you'll drawing like a pro in no time!