Instructions
Assign Earthcaller to one of the directions on the directional pad. You can assign secondary weapons to the directional pad by pausing the game to bring up your gear menu.
Select the Earthcaller by highlighting it and pressing "A" for Xbox 360 or "X" for PlayStation 3. Pick an empty slot on the directional pad for the Earthcaller weapon. If you have no empty slots, you must replace one of your current secondary weapons with Earthcaller.
Assign the Crossblade to one of the open slots on the directional pad using the same process. When you are finished assigning your secondary weapons, press "Start" to resume gameplay.
Equip the Earthcaller horn by pressing the directional button to which you assigned it. For example, if you assigned it to "Left," press "Left" on the directional pad. To switch to the Crossblade, press the directional button to which you assigned it. Use the directional buttons as necessary to switch between your secondary weapons.