Hit the tilde (`) key to bring up the the text box and type "Iroll20s" to unlock the console commands. Note that doing so will disable steam achievements.

Code	Effect
AddAbility playername nameofability	Adds abilitys (Talents) to a specific player.
AddItem itemname stackcountamount	Adds items.
AdvanceTimeByHour numberofhours	Fast forwards time.
AddExperience amount	Gives Experiance.
GivePlayerMoney amount	Gives money.
RemovePlayerMoney amount	Removes money.
AttributeScore playername attributename amount	Sets base attribute score.
Skill playername skillname amount	Sets base skill score.
SetTime timewanted	Sets time (1 for 1am, 14 for 2 pm)