This classmate did not join the website. Therefore his name is not on the In Memory classmates list. Instructions say I have to make him active and then his name will appear on that list. But how do I make him active???

When you used Edit Site Pages to go to the In Memory page, you can add someone - even if they've never joined - as long as you have added their name to the classmate list.

To make a member active so he/she can be added to the In Memory page: Edit Site Pages > Enter/Edit Classmates > Click on Edit Details for the classmate of interest > Enter Contact Information for the classmate > SAVE CHANGES. Now, when you click on Edit Site Pages > In Memory > Edit Page for Classmates > Select Below, you'll see the classmate's name.

Got it! Thanks! I made it work.