After purchasing the Pro version, you will get a zip file (woostify-pro.zip) on your My Account page.
You can install the Pro version like doing with a normal plugin by going to Plugins > Add new > Upload
After activating Woostify Pro plugin, just simply go to Appearance > Woostify Options and you can see the options to enable all the pro modules here. You can also disable the module that you don’t want to use.
You can see a blank to fill the license key on the sidebar. This Woostify pro key is for activating the update and support feature.