@xXRaDsKiXx If you are talking about if you need to add something to show that you drew an OC for someone else and aren't just submitting another OC, then I believe you would need to add something to the description of the post explaining it, or just let the person that you are drawing the OC for post it themselves.
@xXRaDsKiXx Tag yourself as the artist, tag the OC name. The OC name should already be connected to the account it belongs to. Add his name in description to be sure. Also, tag the collab. 2018.
"Hello, Thanks for applying to have your OC flying in the community collab image. Unfortunately, your request was not approved due to the number of submissions we got. However you are still welcome to submit your OC in a standing or sitting pose, and we’d like to see what yo come up with! Joey"
I'm just gonna repost this for any artists who want to help, or anyone who needs help drawing their OC. I would also read the first post to get good insight of what to do.
This may be a silly question, but if a piece is submitted for the collab, is it allowed to be submitted as a stand-alone piece on other websites, like deviantART or the like? Or should it remain exclusive to derpibooru?