Hello, and welcome
You can get tickers from various places. If you google 'weight loss ticker' you should get a few results. Otherwise click on my ticker (or anyone's) and it should take you to the site I/they use.
Once you have the code for your ticker, you need to copy and paste it into your signature (this is accessed via 'User CP' at the top left hand side of this page.
You only have a certain amount of signature space to begin with, but as you post more, you'll get more space to add goals, pictures or whatever you want!