Create an account at https://console.ng.bluemix.net/registration/
This will set you up with a 30 day trial. You don't have to pay anything for the free resources and you don't have to set up billing until the end of your trial (though not all services will be available).
This is optional, you can perform most actions via the web console from step 1. The CLI utilities can be downloaded from https://new-console.ng.bluemix.net/docs/starters/install_cli.html and you should install both the bluemix cli and the cloud foundry cli.
$ bluemix api https://api.ng.bluemix.net
$ bluemix login -u username -o org_name -s space_name
You need to specify your username, org_name, and space_name which you can get from the web console in Step 1.
After you log in successfully, you have now setup bluemix. You can learn more about the CLI and get additional plugins from http://clis.ng.bluemix.net/ui/home.html