If you want to add an external website to your personal staff information you would go to the staff information area, fill out the staff info, and look for the place where you would add a person link. Put your website there and it will show up on the bottom of your personal info.
If you want to add an External Link anywhere else in your Bb classroom, you can do it from within any content area by clicking on “Add External Link”. You can also have a Navigation Button for External Links if you want them all in one location in your classroom.