On the left side of the league pages
( http://www.myleague.com/teamaml/ )
 are several links which change the content of the main frame. Click on the link 'REPORT LOSS' to report a game in the league. The main window of the page will change itīs content to either the sign in page or to the choose teams page if you are already signed in.

The name of your team usually already is showing up, so all you have to do here is typing the opponents team name, then click on Select Players button.

After clicking the Select Players button you will come to this page. Here you select all 4 players in the drop down boxes. If there was a guest a table you add a "Match comment" as follows: "thanks to 'name of the guest' as __GUEST",
then enter your own nickname and password, before you click on 'Submit this loss' button.