The notice you posted isn't from TurboTax, it's from the IRS and only delivered through the TurboTax program to tell you why your return was rejected by the IRS.
The five digit 'signature pin' that is asked as part of the identification process during the filing steps is self-selected. It can be any set of five numbers, but you're the one who picks them. It's not necessary to remember them from year to year, but if you do, they can be used as part of the verification process for next year. Otherwise, you can use the prior year AGI from your return for that step.
The notice from the IRS relates to something called an Identity Protection PIN - which means there was a past issue with potential identity issues at the IRS. That is a six digit number that will come via a letter each year in December or early January. The rejection notice below says the number entered for the spouse on the return was not correct. You can go to the IRS web site to verify the IP PIN at: www.irs.gov/genanippin
