There are two ways of creating transactions: during transaction entry and via MoneyWiz Settings. Please remember that in order to use tags, you need to have them enabled in Transaction layout settings.
Creating tags during transaction creation
To create tags during transaction creation, start creating a new transaction or modify an existing one and then type in the transaction tags field. If the tag you've typed does not exist, it will be created.
Creating tags via MoneyWiz Settings
To create new transaction tags, first go to MoneyWiz Settings by clicking on the gear icon in the menu. Once you're in Settings, click on Tags section. To create a new tag, click the + button and enter a name.