On the Homebase, you go to the "Tools" menu and then "License Products".

However, did you purchase the 2017 program, or is 2018 your first year with ProSeries?  If 2018 is your first year and the "Tools" ... "License Products" does not work, you may need to contact the sales department for them to 'give' you 2017.

https://accountants-community.intuit.com/articles/1617365-proseries-hours-of-operation