How to I add a player token (character) to the scene?

Open the hierarchy panel
Press the "Add Token" button
Select the character option
Either select and existing character in the campaign or add a new character and upload an image for the character's appearance
Your Character will appear in the scene
To assign the character to a player select the token, go to the token details sub panel, click the settings tab (the one with a gear) and choose the player from the dropdown.