Have you downloaded the pro version files from purchase receipt email ? You need to download it and upload it from plugin upload section. Once it is activated you will have the same menu in wp-admin as lite version. Please make sure you remove the lite version before activating pro version.
Thank you for your quick reply at my personal e-mail. As I can not reply the Masonry e-mailadres, I’ll ask my question in this forum:
I did not receive a purchase receipt e-mail yet. Just one that states my username and password (that I entered at checkout). I payed with Paypal. Could that be part of the problem? How many days does it normally take to receive a receipt e-mail? I would like my website to go online this week.