it's quite simple really.
When you have the text capsule open and you have written text, highlight the text that you want to use as a link to somewhere else like another one of your hubs or any other website in the internet and click on the connected chain near the top right hand corner.
When you click on the connected chain, not the broken chain, another capsule will come up. In that capsule you can choose any one of your hubs or paste any other url into the empty space provided.
Best thing to do is to try it out first and practice with it, that way you will learn to use it better.
I hope this answers your question.