go to the 'my chart' page.
Click on 'sharing', then 'set up home page'.
on the home page set up screen you will be able to enter some info about yourself (most of us have a blurb that says I am xx years old, DH/OH is xx years old, and we have been TTC since month/year'). Right at the top of the page is a box marked 'Homepage URL address' or sth similar - if you select and copy the URL that appears in the box below, you can then paste it into your signature file on here, and/or into a post.
Whilst you're on that set up page, you can click 'preview' just above the URL - that will take you to the page that everyone else will see.
HTH, welcome!