Say for example, on your SB You site, you'd like to have a link to Blackboard that opens into a new window or tab when a user clicks on it.   And you'd like this link to be in the Menu bar of your site:

1. Create a New Page by going to New > Page.   Then give it a name and click Publish - No other content necessary.
2. Now go to Appearance > Menus in the dashboard
3.  You will see the new page in the Most Recent tab of the Pages section.  Check it off and click Add to Menu.
4. In the Menu Structure setting, drag and drop to move around the order of the menu items.
5. Now you need to turn something on in your screen options on the top right of your screen.  
6. Click Screen Options > check off Link Target.
7. To make the Blackboard page open in a new tab or window, click the down-pointing arrow ▼ next to Page
8. Check off "Open link in a new tab/window"
9. When finished click Save Menu