Links are always a good thing; sometimes you want to link to an external destination, and other times it will be within your own site, or to an email address.
All of it can be done through the facilities of the Content Editor.
All you have the do is highlight the text you want to create a link for by dragging your cursor over the text. Then go to the "chain link" icon that you will see in the Content Editor text toolbar.
At that point, you'll have a "Link" dialog box.
You'll have the chance to link to an anchor in the text (which means you'll link within the content itself), or to an email address, at which point you'll be asked for the proper information.
You can link to a a page within your site, as long as you know the URL. Essentially the same thing goes for a link to an external site.
The "Protocol" comes before the URl, whether it is "http://," "https://," "News://," "ftp://," or "other." make sure you have the correct one chosen from the drop down box, or your link will not go where you intended.
There is also a "target" designation. This allows you to choose whether you want the link to a new window, a parent window, a frame, a popup, a topmost window, or the same window. You may not be familiar with all of this, so you may want to experiment a little to see what they all look like.
Remember that no link is going to be any good unless you save your work, so make sure you do that.
If you want to make any changes, right-click the link in the Content Editor and you'll be presented with choices to "Edit Link," in which you can change what the link does, or "Unlink," which allows you to cancel the link altogether.