How can I indicate to CRA that I am using special provisions to contribute to RRSP without using RRSP contribution room, like when I withdrawn from a HK retirement plan?

Enter the amount you withdrew, then enter the RRSP contribution, making sure to enter the transferred amount in the box "Is this RRSP contribution a designated transfer of eligible income amount? If so, enter the amount that is a designated transfer".  And that should do the transfer.