The answer you seek, young Wizard, is right in the Help & Support section.
If you are unable to use the chat function It is possible that your account does not have Filtered Text Chat enabled. Accounts set up as over 13 players are able to use the Filtered Text Chat.
If you have an account that is over 13 and can still not chat you might need to enable the feature. To enable you must login to Wizard101.com and select "My Accounts". Under the "Account Management" section login to your parental controls and click on the 'enable' button located next to the 'filtered text' option.
Filtered Text Chat for players with under 13 accounts can only be turned on by a parent/guardian over age 18. The parent/guardian must validate his/her age by buying a subscription or crowns with a valid credit card.
Open Chat is for players with age 18+ Subscribed accounts. The player must validate his/her age by buying a subscription with a valid credit card.