The Greenhouse integration is a webhook that syncs candidate data between the two systems. Step-by-step instructions on the technical setup can be found here.
Once the integration is set up, you will be able to push new hire information to Remote at the Offer Stage in Greenhouse. So when you click on the profile of one of your candidates that you are ready to hire, you'll select the "Offer Details" tab and one of the two buttons - create offer or mark candidate as hired. On the pop-up form, you'll select Yes within the "Send New Hire Information to Remote for Onboarding" field.
Within your Remote account, if the candidate already exists then their information will be updated. If they don’t exist (which will be the case most often) then a new profile for the candidate is created in Remote.