In order to access an STYLELABS development sandbox, you need a STYLELABS support account. How to sign up for a STYLELABS partner account, can be found here.
After your account has been created, please follow these steps to enable your account.
Step 1: Browse your development sandbox.
The url of a development sandbox looks like this: http://******-sandbox**.stylelabs.io
Step 2: Select SSO provider.
Use 'Sign in with SSO' to authenticate.
Step 3: Authenticate
Use your STYLELABS partner account to authenticate.
You should know have successfully logged in into your STYLELABS development sandbox.