Once you enter an amount in the box "Enter your unused RRSP/PRPP contributions from line B of your "RRSP/PRPP Deduction Limit Statement" on your Notice of Assessment, Notice of Reassessment or Form T1028", you must say "Yes" to continue.
Enter in the amount from your NOA here, then when you continue to the RRSP CarryForward page, you will have the option to claim all or portion of this amount.