Dont know how to upload files to mybook live...Help?

Hello All,

First post here. I have a Mybook live 2tb from a long time ago and I never really use dit much and for the life of me cant remember how to upload files. I am able to access it with my PS4 and my desktop and see folders. On my desktop I can make new share folders but for the life of me I cant figure out how to upload files to the share. I am able to drag and drop a file from the MBL to my desktop but I can not upload a file or drag and drop any file form my PC to the MBL… Am I missing something here? I need to upload a backup of my Dropbox as I accidentally deleted some folders and luckily still have them on my PC as I have disabled the sync. I want to upload my entire dropbox from my PC to the MBL to preserve it just in case ths sync wipes out these folders… Please help as I need to save these files…

Ok so I was able to access it with my original laptop running windows 7. This is the machine I set the MBL on orriginaly. Now my question now is, how to I give access to my new desktop and other computers I have to read and write to the drive?