You can upgrade your plan here
You can purchase additional Feeds for your current plan directly from your payment information section here. Simply click "Edit Options"
And then select "Add Feeds". You will then choose which IG social profile you would like to add your additional Feed(s) to. (which will bring you to the payment screen to complete your purchase.)
Each additional feed is billed at $5 per month (or $45/addtional feed yearly)