As Doug said, you will either have to buy a 2013 product key to activate the trial you have (if you can find someone still selling 2013) or if you are lucky you will be able to take advantage of the free Office 365 Education offer:
Office 365 Education / Student Advantage
Dec 1 2013 - “Student Advantage” - Free 365 Pro Plus at schools that have site license for
http://blogs.office.com/b/office-news/archive/2013/10/15/announcing-student-advantage.aspx
http://www.microsoft.com/en-us/news/press/2013/oct13/10-15skillspr.aspx
<snip http://www.theregister.co.uk/2013/10/16/microsoft_office_student_advantage_program/ >
The software giant on Tuesday announced a new program called Student Advantage, whereby students worldwide can sign up for subscriptions to Office 365 ProPlus through their institutions at no cost to themselves.
The only stipulation is that the schools must have already licensed either Office 365 ProPlus or Office Professional Plus for their entire workforces, including faculty and staff.
</snip>
So talk to your Help desk to find out if this applies to your school
<snip http://office.microsoft.com/en-us/academic/ >
2012 06 27- Free Office 365 for education bundle now available
http://www.zdnet.com/blog/microsoft/microsoft-office-365-turns-one-education-bundle-now-available/13032
MS Rolls Out Office 365 For Education
http://www.informationweek.com/news/software/productivity\_apps/240002794
June 27, 2012. Office 365 for Education gives students free access to online versions of Outlook, Word, Excel, and PowerPoint, and allows them to connect to each other and to their instructors through cloud-based editions of Exchange, SharePoint, and Lync.
Free Office - Signing up for Office 365 Education****
Using your school-provided email address at http://office.com/students or http://office.com/teachers is the quickest, easiest way to get started using free Office tools for your school work.
There could be a number of reasons why you are unable to sign up:
- We are not able to verify the email domain you are using
- Technical issues caused by various existing user directory configurations
- Your school may have turned off the ability for students and teachers to sign up themselves
If the message you receive after a failed attempt is one of the first two – keep checking every week. If your school is restricting student/teacher sign ups, or you don’t have an email address provided to you from your school, you should check with your
school to get information on how to proceed.
If you have additional questions you can post them in the Office Applications forum.