To view transactions click on 'Transactions' icon at the top of your screen.
Clicking on any transaction will direct you to the tag shown below. You can tag the transaction at top level by tapping once on the tag shown and then again on the green box that appears. To open up a second, more detailed, level of tags tap on the arrow to the right. Alternatively, you can search for a tag by clicking on the magnifying glass in the top right of your screen.