Storing an Itunes Library on an External Hard Drive

I am using Itunes on an older device that is running an outdated OS. I have my full library, organized by playlist, in Rekordbox (I prefer using Itunes to organize music, then connecting to Rekordbox to load onto flashdrives for mixing). So, I want to bring my library back to itunes. However, I don't have space on my macbook, so I need to keep the library on my external hard drive (I have done this before). I want to copy all of the files from Rekordbox, into a new itunes library file that is stored on my hard drive, so that when I connect the hard drive to the mac book, I can open itunes synched to the files on the hard drive. I need some guidance with completing this transfer.