As far as a free user is concerned, there are two ways to deal with it. The first one assumes your character sheet doesn't have a defined token for it and uses the character's picture as a token. If that is your case, all you have to do is change your character's picture and his token will be updated. The second one involves using rollable tables as tokens. You will need to remake your whole token setting, but only once if know what you will use in the future (and you can even use it for shape shifting). First you'll have to create a rollable table for a character in the collections submenu on the top right side of the screen. Then you name it and add and a number of items with possible pictures of your token. After that you'll have to set things - bars, auras, lighting sources and linking token to the sheet - for your token again (but never again after that). If you want to change the character's token from that, all you have to do is right click it and select "Choose Side" to the appropriate image. Video reference. Hope this helps.
