If you only want to allow participation for a selected group of people, you can set a global password for the survey.

Please proceed as follows, to set a global password for the survey:

Select the desired survey in the Overview
Click on Settings
Go to 'Access Control' select the option 'General password'
Enter a password
Click Save settings

Once you have saved the settings, participation in the survey is only possible with the password. For the survey preview the password will be required, too.

Note
If you have activated the option 'General Password', the e-mail invitation tool will automatically set the placeholder for the password, as long as you have not changed the default text until then. Please check the correct filling of the password placeholder with a test email, before you start inviting.