First things first, you need to be logged in as the admin of the WordPress blog you are about to edit. Make sure you are in your dashboard.
Click on Appearance then click on Widgets. Under Widgets, look for Text (Arbitrary text or HTML.) Paste whatever text you want in there click save or add if you are updating. To make space for the next time you may want to add you can add returns, which are <br> tags. I usually add two so there is a larger space between each.
You can add a title to your addition but know that whatever you title it, is visible.
This is great for creating things you are a part of, or even want/need referrals.