On Yahoo messenger, how do I customize "my station" on LaunchCAST?

Short answer: Go to music.yahoo.com. Sign in if you aren't already. Use the Search box at the upper right to search for artists, albums, or songs that you want to add ratings for.

To add or change genre ratings, go to your main station page by clicking on Radio > Edit My Station from the tabs near the top of the page, or click on your statin from the My Music box on the right hand side of the page. Once there, you should see a navigation bar on the left hand side where you can click to see all Launchcast genres. You can rate them there. You can also click on "Artists", "Albums", or "Songs" to review what you have already rated. You can change or delete your ratings for those items there, one at a time.

To delete any rating, find the item that is rated and double-click on the rating bar (either the stars or the numeric scale, depending on which you use). Double-clicking makes the rating go away.

I hope this helps get you started.