Transaction Tagging can be done from mobile or web browser.
Mobile App -
You can tag a transaction from the Transaction Details screen, which you access from the transaction you wish to tag.
The Add Tag option is located half way down the screen. Select the tag icon and then enter the tag title into the provided input field.
Web browser -
Tags are added to transactions from the My Transactions screen by clicking on the transaction that you wish to tag.
The tag field is located halfway down the page to the right of the middle. Type the name of your tag in the field provided. If you have already used the tag, it will appear as an option as you start typing.
You can delete a tag from the transaction by selecting the cross icon next to the tag.