you should prolly be able to use the jibbin forums by tomorrow... although you may not even need to be a member to read their guide on how to install custom levels...
simply download. right click on the file, press extract here or whatever. open that file, right click on the file ending in .b3d, press cut, go into your Jibbin folder in program files or whatever, then go into custom levels, and you should find a folder in there with all the other .b3d files, then just paste it there.