A cooperation agreement is a three-way contract between the author of the thesis, project subscriber and the supervising teacher. Look up the details from the thesis cooperation agreement (Finnish or English) or from the thesis manual.
If you’re making a thesis for your own company, an agreement is not necessary. A thesis cooperation agreement is handled in Wihi like this: send a message in Wihi to the thesis subscriber and supervisor, and attach a filled-out agreement. You can attach the agreement to the message by first bringing the file to Wihi (click add file).
After that a “send for external comments” button appears below the file. When all participants have agreed to the contract through Wihi, the contract is accepted. The message chain serves as proof of contract, and it is archived in Wihi under "Statements by interest groups" (in Finnish "Sidosryhmien lausunnot"). The section will appear on Wihi after the first message is sent. Make sure to notify your supervisor as soon as you have received a message of confirmation from your commissioner since the supervisor will not get notified automatically.
After this phase you have completed stage 1/3 of your thesis, which will be registered to Wihi.