Visit jalbum.net and click "Sign in". Sign in with your username and password.
Click the tab with your username on it to see all the albums on your account.
Find the album you want to delete and hover the mouse over its thumbnail image to make an options menu light up. To delete your album you must first go to the "edit" page by clicking "Edit album".
On the edit page there is a "delete" button in the lower right section. Click it and the album will be deleted and removed from the Jalbum.net community.