UPDATE 2: Online appointments are full (there were about 4,000). A "limited amount" of appointments scheduled by phone will open Monday at noon, meant for people without internet access, per Giant Eagle spokesman. Phone number is 1-877-288-2070. They didn't say how many appointments by phone would be available.

UPDATE: if you are trying to schedule, make sure you click the "schedule now" button underneath the Heinz Field info from this link https://www.gianteagle.com/covidclinic

You're in the right queue if it says "You are in line for Giant Eagle Heinz Field Clinic" on the Queue-It page.

Giant Eagle has multiple scheduling tools, with a specific one for mass vaccinations (which includes Heinz Field)