Go to desk.zoho.com.

Select a ticket or email.

Once you have it open, you will see different categories like shown in the picture on the left side.

On "Link to Case" you will see the link that will take you to the ase in CRM. Once you click on it, a new window will open.

(That window will show the case in CRM.)

If you don't see a link, it means that the student sent the email from a different email address that is not on their case. If this is happening, use the student's name to find the right case. 

Instruct the student to only use the email on file to send emails to avoid miscommunication.