You can purchase from the Appliances > Small Appliances section of the catalog.
Clicking on the press will allow you to select from several different crafting menus. Once you've chosen what you want to make the press will start working for about 60 sim minutes until it's done.
This press works off-the-grid so you don't have to worry about powering it. As this appliance slowly presses ingredients you'll see the lid get lower and the bucket fill will liquid. The bucket will be filled to the top when it's finished but you can always hover over it to see how long before you can collect the finished product.
Once the press has finished you can click on it and choose to package your ingredients. Your sim grab their newly crafted ingredient from the press and put it into their inventory.
Please keep in mind you must have the custom ingredients installed for these crafting menus to show up.