To create the 'Parallax' element you need to choose it in 'Grid Elements' tab when creating a new element. (2.4.1)
In the 'General' tab you can see that the content element type 'Grid Element' (1) and grid layout 'Parallax' are selected (2).
The element also uses the regular header field (3) and a link field (4), where you can insert the site or page you want to link to. In the field 'Plugin Options' you are able to set the height of parallax element (5). When this field is set to 'Auto', the height will adjust to the content inside. (2.4.2)
In the 'Appearance' tab you need to add a file - which will be the background for your 'Parallax' element - for example a picture uploaded to 'Filelist'. (2.4.3)
After you 'close and save' the 'Parallax' element, you'll see the area where you can add a new element (it can be some header and text with the use of for example 'Regular Text Element'). (2.4.4)