The discussion kind of drifts away from the original topic, but be assured that we’re happy to help. 
To sum it up:
If you have basic IT knowledge, you can follow the standard install. You’ll also need a domain name, and configure an email sending service such as Mailgun (tutorial here: Configure Mailgun for email when using Digital Ocean for DNS).
Note that we usually won’t help on matters that are outside the scope of this forum. For example, the question “How do I register a domain name?” wouldn’t fit here.
If you don’t have basic IT knowledge and depending on your budget, you can ask for paid support on marketplace.
Finally, you can also have a look at Discourse managed paid plans, where pretty much everything will be handled by us and you’ll have access to our team support.
Also, know that we provide discounts for educational purposes, since you mention it’s for your school:
Are there educational or non-profit discounts?
Yes! If you are legally recognized as an educational institution we offer an 85% discount. If you are legally recognized as a non-profit organization that is exempt from federal taxes, we offer a 50% discount. These discounts apply only to our basic, standard, and business plans, cannot be combined with other discounts, and must be paid through a debit/credit card monthly or annually. Please contact us after starting your trial and we’ll add the discount to your account.