Transferring iTunes

So I was trying to backup my iTunes library by copying it to an external drive by following the instructions found here: Back up your iTunes library by copying it to an external drive - Apple Support. However, when it came to the part about holding down the option key while opening iTunes to get to the "Choose iTunes Library" option, iTunes opened but that option didn't pop up. Then I tried to copy and the backed up file into the iTunes folder, which seemed to work at first but when I opened iTunes none of the songs were there. Any ideas?