What once was a totally separate function has been combined into the functions of the one big paste-your-spam-into-the-box form. The single-line entry mode is for looking up a reporting address target for things like IP addresses, e-mail addresses, and/or Domains. This would normally be used in generating your own manual complaint/report, looking up data for inclusion in the comments of a SpamCop generated complaint/report, or for a number of other reasons for reseaching something <g>

Log into "your" www.spamcop.net web page.
Paste in your copied IP address, e-mail address, or Domain name.
(single line entry only, no C/R, no Enter key-press .. if the data is longer than the box is wide, it may wrap, but that's still seen as a single-line entry)

IP address looks like: 192.168.33.107
e-mail address looks like: someonefamous[at]invalid.com
Domain looks like: www.example.com

Click on the "Process Spam" button
The next screen wil show you some of the parsing logic used to track fown the "ownership" of the data submitted, a bit of history/status on the item submitted, and the identified / best-guessed reporting address.

One caveat, due to the parsing mechanisms involved, some results may return an entry that was manually entered into an "over-ride" database. The over-ride may be to the upstream of the entity involved or it may be an internally used SpamCop routing address. Please do not attempt to use an address that contains "spamcop" (most of those attempts will end up being rejected as they won't be coming "from" SpamCop so you'll simply be wasting your time) ... if that is the only resulting address, you'll need to use another tool to find a reporting address [suggesting the Research Tools Forum]