conditional formatting inquiry

I am currently trying to learn how to use google scripts but I don't quite fully get how to use conditional formatting for a task i was given.

This is a part of the task:

"A script to see who is eligible for scholarships for a free degree! Before you do so, go back to the sheet and create a new column on the spreadsheet with a header ‘eligibility’ Your script should then figure out if the student has above 80% attendance and be earning less than 30,000. Print in the cell in the relevant column to say either the student is eligible or not."

So I have 2 bits of data that I need to conditional format but only using google script that is linked to a google sheet. Not fully sure where to start and would love some help getting started with this.