If this is your first visit to the introduction page when you click on your first name the wiki will tell you that the page does not exist and do you want to create it, select yes!
You will then be automatically put into the editor. Type some text and then select save (at the bottom of the page) and you will see the page as others will see it if they visit your page. You can then select edit and continue to work on your introduction. You can change the name of your page by editing the test in the Title box above the menu with the various edit options.
You can compose your text in your favourite word processor and copy and paste it into the wiki but you'll need to do the formatting using the wiki wysiwyg editor.
And you can also add a tag or two to your page which will show up on the site's tag cloud. If you want to use a short phrase, e.g. classroom management as a tag then you need to connect the two words, i.e. classroom_management. The tag software interprets a space as a separate tag.
The main thing to remember is that you can't do any damage. The wiki keeps a history of pages. You can always go back to an earlier version or restore a deleted page if you manage to accidentally delete one.