Since we do not have a tool for recording buy/sell trades since the changes on the website we executed in 2011, what you can do is to go to your portfolio and then click on "Add/Edit Symbols." Here you can enter the number of shares you bought under the "Total Shares."
For example, if you bought 1000 shares of V.INT, just enter 1000 under Total Shares. Scroll down and then click on Save.
In case you sold 600 from these 1000 shares, you can go to Edit Portfolio again and enter 400 under Total Shares and then go to the far right of the row and indicate that you have sold 600 on the Notes Tool. From here, click on 'Save."