ARIS REST API

Hi, I am new in ARIS. I have ARIS Connect Server Access Infrastructure license key for ARIS 9.8.
Please, explain what it means (from  http://localhost/apidocs):
"The token must be included in all subsequent API calls as URL parameter (umcsession) or added as cookie to the HTTP request.
POST http:// <servername:port>/umc/api/tokens?tenant=default&name=system &password=manager&key=lsjflskjfsfj
The parameter key is the string representation of an X.502 certificate."
Where I can get value of a parameter key? Thank you.