Jetstream is accessible through a web interface https://use.jetstream-cloud.org using XSEDE credentials via Globus Auth. Jetstream is not accessible via XSEDE's Single Sign-On Login Hub. Newly created XSEDE accounts must be added to a specific allocation by the PI or Resource manager in order to access Jetstream.
Jetstream allocations are awarded exclusively through the eXtreme Science and Engineering Discovery Environment (XSEDE). XSEDE provides XSEDE User Portal (XUP) accounts free of charge.
To get a Jetstream Trial Access account, please see Get a Jetstream Trial Access account. These accounts have limited resources available but allow you to try Jetstream
To get a more full-featured account, you'll request a startup allocation, please see Jetstream Allocations for step by step instructions.