1) Go on this page: https://hubpages.com/my/hubs
2) Click the "edit" button next to your hub
3) Scroll down and click "edit" on any of the capsules you wish to edit.
In your case, you can also add new "text", image or any other capsules capsules by clicking on the capsule options that are given under "Add More Capsules" and that capsule will be added in your hub,
Once you have added a text capsule, then all you have to do is to again click "edit" in that capsule and start adding content.
hope this helps!
I hope I havent confsus