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Open Service Setup in Salesforce:
Click on Users > Users:
Create a new user and choose for System Administrator* under Profile:
*We advice you to use a copy of the default Salesforce System Administrator Profile and disable the expiration of passwords in this profile! See Manage Password Expiration with Password Policies and Permission Sets on help.salesforce.com.
Log in with the new user and create/reset the security token. See Beveiligingstoken ophalen Reset security token in Salesforce or Reset Your Security Token on help.salesforce.com.