You just have to push edit button on the hub where you want to place your link. Then, decide which part of the hub should the link be. It is better to place it at the end. Then by placing a cursor at that part of the hub you should see a small sign 'add'. Push it. A bar appears with various widgets. One of them is 'link'. Press it. A link capsule appears. Push edit. Then choose 'add links by url'. Then place url of the hub you want to place link to. Then you will see three things: link url, link title and link description. Most probably they will be filled. If not fill them in. Then push save. That's it. You have linked your hub with another hub. Then you can repeat the procedure. I hope that helped.