Adding links or tabs to your main menu is easy.
Step 1
Make sure you create a Collection first under the Collections tab.
Step 2
Select Navigation then click Add Link in the list in which you wish to create the link (usually Main Menu but could be footer or another link list if you wish).

Step 3
Give the link a name (Collection 1, in this example) and then use the "Links to:" drop down to select the type of asset to link to, in this case its "Product Collection". It could also be a blog, a product, a catalog, etc. Select the Page you want to link to, in this case it is "Notepads".

Now you should notice the new link you've created is in your Link List you created it in. If it's not, go back and create it again following the steps above.

Note: You can also put this in the footer, which would look similar to this...

