Keyboard - Press ALT + A on the keyboard. The "Add to Favorites" should be highlighted. Hit Enter. Use the Tab and Arrow keys for Choices. Then highlight the OK button with the TAB function when finished and hit Enter.

Mouse - Click on the Favorites Menu. Choose Add to Favorites. Choose Location. Click OK.
 

Keyboard - Press CTRL + D on your keyboard - once. The bookmark will show up 
at the end of your bookmark list.

Mouse - Click on the Bookmark Menu. Choose Add.
 

Here's three ways to Bookmark in Opera. Two using the Mouse, one using the Keyboard..

Keyboard - Press CTRL + T or select the option from the "Bookmarks" menu. The bookmark will be added to the currently active folder.

Mouse -This Way - Right Click on Page in View. Choose "Frames - Add to Bookmarks". The Bookmark Properties will be displayed. If you wish, you can type a "Nickname" or "Description". Click OK.

Mouse - That Way - Click on the Bookmarks Menu. Choose "Add current document here..". If you wish, you can type a "Nickname" or "Description". Click OK.

Keyboard - Press CTRL + D on your keyboard - once. Click OK.

Mouse - Click on the Favorites Menu. Choose " Add to Favorites". Choose Location. Click OK.