Aperture Question?

Ok, so i installed aperture for mac on my MacBook and selected the path of the library as the one on my iMac so it would be the same as the library on my iMac. However when i went to relaunch Aperture it said that this path is not valid and i needed it to be on the local disk. However when i click ‘ok’ it closes Aperture and i have no way of changing the path. I tried deleting and reintalling the app but this keeps the old data, i.e. the old path… How do i either change the path or completely wipe the user data so it is like new.