K2 can use multiple authentication Issuers. The most common are Forms and Windows Authentication. We can choose which one we would like to auto login with.
#1. Navigate to K2 Management.
#2. Open Authentication > Claims > Issuers.
#3. You will see a screen similar to this.
#4. Select which Issuer you would like to use and click Edit.
#5. Check the Use For Login and click ok.
Now this issuer will be default issuer we use for logging in to Smartforms.