This article shows new users how to login to a Salesforce sandbox environment.
When you've been setup as a user in a sandbox Salesforce environment you should receive an email triggered by your system administrator, the email will provide a link that allows you to set a password and login to your test environment.
To login after setting your password, open a browser and go to https://test.salesforce.com.
Your username in most cases will be your email address with the name of the sandbox added to the end. For example, if the sandbox is called "dev", then the username will be "firstname.lastname@example.org".
Your password will be whatever you've set it to be.
Google Chrome is the recommended browser for accessing Salesforce.