Tabasci is a tablature editor, not just a text editor used to write tabs. It understands the underlying structure of a tab so it can give you the tools to easily produce them. Everything in the tab can be represented by simple text so you can always take your tab in plaintext and put it wherever you want. You should understand the basics of tablature before using this site.
You can get started immediately by creating a new tab. Register an account and save your tab so you can come back to it later. All the tabs you've written will be shown in your account page, where you can also set or change your public username.
Visit /browse to see other tabs that have been made public. Make your own tabs public by to allow others to see them.
You can use the tutorial to learn about the features of Tabasci and how to use them.