In order to view your Charms, click the ‘Charms Arena’ tile located in the main lobby and choose a set. At the bottom of missing Charm, you have the option to “Ask for Charm” from other players. If a Charm is grayed out, it means you haven’t collected it yet.
 
Note that not all Charms can be traded, restricted charms (golden frame) will not have a trade request button on top of them.
 
At any time you can access your trades. You can check the Trading Center, next to the packs' button at the bottom of your screen.
 
 
Each successful Charm trade transaction will consume trade tokens. The amount of trade tokens may differ, depending on the rarity of the Charm you wish to trade.
 
 
You are able to request as many Charms as you wish as long you have enough Trade Tokens required to complete a trade. Your trade tokens will be consumed only upon making a successful trade. However, you can perform up to limited number of successful Charm trades per day.
 
To learn more about How to Get Trade Tokens? - please visit this FAQ article.