T777: I work from home. I have to claim rent, internet and electricity. I’m confused by HST and GST part of the form. Where do I add my rent? Do I add internet under hst?

Electricity goes in the box labeled "Electricity, heat, and water". You can add rent & internet as an "Other" expense. You would choose which column to put your expense under based on what type of sales tax you paid. Residential rent is generally exempt from sales tax.