First of all, select the element or text you want to link to. Next, click on the Link button that will appear above the element or text you highlighted.
In the window that will appear, set up the page where the element or text will link to. It can be an external page or a page of your website. Also, you can specify where the linked page will be opened, in the current window or in a new one.
If the Link button does not appear, it means that the element or text can't be made clickable.