To connect your Instagram accounts to Postcron for notification reminders click on the + sign button at the top right side of the screen, and click on Instagram. Then, select Personal.
You can use notification reminders for all types of Instagram accounts, including private ones. If you're looking into connecting Business accounts to post automatically to their Feed you can do that too. Learn how here.
You will see a pop-up explaining how posting with notification works. After reading it carefully, confirm by clicking Ok, Add my Instagram account.
Then, name the account and click on Continue.
The name doesn't necessarily need to be the same as the account's username, just make sure it will help you easily identify the account once you get the notification. Especially if you manage more than one account, as you'll need to know if you need to switch from one account to the other on Instagram. You won't be asked to log into your Instagram account or enter your username and password whatsoever.
Now confirm by clicking on Add Account.
All the social accounts you connect to Postcron will be displayed on the upper part of the screen. If they're Personal accounts, you will see the Instagram logo alongside a person icon to help you differentiate them.