Create a Redshift cluster as described here:
Add Segment's IP to the cluster's allowed IP list
Make sure at least one of your Segment Sources is sending data to the newly created warehouse.
Add Chartio's IP to the cluster's allowed IP list
Get your schema names. You can get them from each Segment's UI, from the Source page under Settings > Sql, or you can get them by connecting to your database via PostreSQL as follows:
a. Add your own IP to the cluster's allowed IP list
b. Connect to your db:
psql -h <yourcluster>.<yourslug>.<yourregion>.redshift.amazonaws.com -U <yourdbusername> -d <yourdatabasename> -p <yourport>
c. List your schemas
Connect chartio with Redshift!