To see what transactions you have already completed, begin by clicking on the account name in the upper right hand corner of the page.
In the upper left hand corner of the My Wallets page, you will see two options. The one that comes up immediately will be Balances. By clicking on Transactions you can change to that page.
This page will be broken into two large frames. On the right hand side you will see a list of completed transactions.
Here you may sort your transactions in a number of different ways, or use the search box if there is something specific that you are looking for.