1. At the same screen where you slect DEPLOY, there should be CUSTOMISE up the top. That will take you to the loadout customisation screen. You need to have unlocked the attachment before you can equip it.
2. You have to equip the GUIDED SHELL via the same process as 1 above. When you are in the tank and have equipped it, it will be your secondary tank weapon. Switch to it (Right mouse button for me) and you will see you HUD cross hairs change from the normal shell to something different
3. sames as 2 but you have to be a gunner to use the TV guided missle.
you have to rank up to unlock things, once unlocked most things need to be equipped and then switched to. Note that tank GUIDED SHELL can only lock ground targets unless the traget is being laser designated by 2rd seat or soflam in which case gorund or air locks are possible.