When you click on the League below a drop-down with the matches for that league will appear (home team listed first) and then you can select the correct one. If you select a match from the wrong league please click on that match again and click on the Select line for that league to clear the entry and then select the correct league.
Having matches from two leagues selected will cause confusion!
Full details about submitting results, dealing with errors etc. can be seen here.
