How do I apply a Massing Preset & a Premium Preset? What's the difference between the two?

A preset needs to be applied to a site (and within site regions):

You can either apply a mass based preset and define buildings/objects on your site with spaces.
A premium preset allows you to solve your site with a specific high-detailed typology and will consume one of your all-purpose site credits.

To apply a massing preset, follow these steps:

Click the Preset Selector at the end of the Site layer.
The Preset Panel will slide out of the right side of your screen.
Enable the Hide Premium Presets option.
Make sure the Massing option and is enabled to see the default presets (Office/Pad/Plaza/Podium - Massing/Structured Parking/Surface Parking/Wrap - Massing)

You can create an unlimited number of deals if only massing presets are used in your deal.

To apply a Premium preset in your site, follow these steps:

Click the Preset Selector at the end of the Site layer.
The Preset Panel will slide out of the right side of your screen.
Make sure the Hide Premium Presets option is not enabled.
Select the building typology you want to be working with to limit the list of presets at your disposal (Housing is selected in the example below).
Select the preset you want to apply to your site (Gurban example below)
You are now prompted to Lock Area and consume a credit. Click Confirm.

You can now create addition sites within the locked area without consuming any additional credits

You have an unlimited number of Massing Presets at your disposal but a specified number of Premium Preset Credits.