The easiest way to do that is just to wait and the log will be automatically truncated for you. You shouldn't have to wait more than a minute for it to happen. If it doesn't happen automatically then there's some reason why log space can't be reused - this will not be resolved by truncating manually.

Why do you want to shrink the log file? Are you confident that it will never grow back to 60GB? If you're not, it's likely that you're wasting resources and causing fragmentation on your disk.

John