torrent is meant to share few files at once, plus if u create torrents of your shared files u'll be the only source, and (i'm kinda new to torrent too) i guess u need to link the torrent u created in some torrent related website in order to have requests from non neoloader users.
u can easily download new files with cross protocol, and this is the only way to appear among the sources for the most available torrent for that file (since creating your own torrent means u won't be part of that), u could even decide to not share files u got from crossprotocol, disabling both ed2k and torrent sharing, letting the file indexed on neokad only, that in practice (i'm pretty sure) will mantain ed2k/torrent assosiation for next neoloaders that will look for that file. this will help you to focus your upload on files that really need it.
long story short... you can create your own torrents for files there is no torrent yet, but transfering TBs of data on your own it's a bit hard.
you cannot be part of the sources of an existing torrent for the old files you had from ed2k, and you can't neither appear as source among them with neoloader if you forget to add btih:hash before you complete the download of that file (before the file be indexed in neokad).
one more thing... some torrents are folders, so the only way to download them from crossprotocol is to add the torrent to downloads first, open that folder in download window and add each ed2k hash to files contained in that folder, with folders this mechanism cant be reversed. with single file torrents the sequence is not a problem.