How do i add income from other businesses within a group not on QB to be used as a float and not to be paid back?

Welcome to the Community Christine!

You can add income to the account in different ways this depends on how you want this to be reflected in the accounts. You can use a Bank Deposit if it is money just coming in to the business, if this is going to go against a specific account a Journal Entry may be a better way of showing this in accounting purposes.

Can I confirm whether this needs to do anything specific within the account?