If you have received an email inviting you to sign, it means that someone wants you to sign a contract via Storegate. Click on "Continue" to go to the signing process. There you can read the agreement and approve it by clicking on Sign in the top right corner and then complete the signing.
Kostar anything to sign?
No, for you who sign a contract, it costs nothing. It is the Issuer (i.e. the holder of the Storegat account) who sends out the envelope pays for the service.