If you have been invited to apply by a foundation/organisation, you will receive an email letting you know about the invitation and an application will available on your dashboard. You do not need to click any apply buttons.
Open the application and fill in the required questions.
Where to find the application
Dashboard style 1
The application will be in the current applications area with a draft status.
Dashboard style 2
You will need to go into 'My Applications'.
The application will be there with an Invited Status.