If a button is greyed out it means that there is a configuration setting which won't allow you to use that button. Examples:
You cannot add recipients to your campaign: because recipients need to be associated with a scenario, you always first need to create a scenario first. After that you will be able to add the recipient group and associate it with one or multiple scenarios within your campaign.
You cannot use the scheduler or other buttons are greyed out: make sure you are not trying to edit the configuration of a running campaign. First stop the campaign and then try again to use the buttons.