Emotes are a way to communicate with your allies and enemies on the battlefield. These are permanent items that do not affect your tank stats in any way.
How to access Emotes
In your Home screen, tap the "box" icon on the left menu to access your Inventory. You will find several tabs for your items, including one named EMOTES.
From the picture above, you'll see the emotes you have active by the little "Green tick" in the corner of them. The emotes that are highlighted are the ones you have unlocked. The greyed-out emotes are the ones you haven't unlocked yet.
How to change/equip Emotes
To equip a non-ticked Emote, tap it and you'll be brought to this screen:
You can then tap the emote you wish to replace. The replaced emote will have a small arrow pointing to it, as depicted in the above screenshot. Once you are happy with your selection, tap REPLACE.
How Emotes Appear in-game
Close to your ammo selector, you can see a smiley face; these are the emotes you have equipped. Once tapped and held, you'll see a wheel to select between the equipped emotes. To use an emote, drag your held finger to the desired emote and remove your finger from the screen; it will then appear above your tank.
My Emotes are gone and I can't use them!
If your emotes are not being displayed in the wheel, you've likely muted them by accident. To fix this, you can hold the smiley face and drag your finger to the microphone button - this will unmute your emotes and bring them back again. The same goes for muting them during the match.