Hi, and welcome to the site.
Harmy’s Despecialized Editions are available in many various sizes and formats - on both public and private torrent sites.
If space on your computer is an issue… there are torrents out there on the internet for the whole trilogy that come to around 8gb in size (a fair few people have them on USB flash drives etc - instead of having them on a disc format).
Please take the time to read some of the threads on the Despecialized Editions on here for more info.
Of course, it a requirement to own the official blu ray release or digital download of Original Trilogy before acquiring Harmy’s Edits.
More info can be found here - Fan Edit / Preservation forum Rules and FAQ