New to the XTEINK x3

Hi guys!

I aquired my XTEINK x3 yesterday and have been trying to set it up. I've seen multiple posts and advice about flashing crosspoint/crossink on the device so I did that but I can't for the life of me figure out how to put EPUBS on the device. I've tried wireless, via calibre and via hotspot. Nothing's working. I get error messages everytime... anyone who can help me out? Are there reliable tutorials somewhere? I've been at this for hours and it makes me feel dumb asf to be fair