Currently, it may not be easy to figure out how to play with the Nocturne Preview Cards on the Dominion Online client. This quick guide will teach you how to do it.
Step 1: After logging in, create a table from the create table option next to matchmaking.
Step 2: Go to Advance Options from the table screen.
Step 3: Select Nocturne Preview.
Step 4: Select add bot to play Lord Rattington or wait for a player join your table. Make sure to have rated game unselected.
Dominion Strategy 
I have followed the directions and selected Nocturne preview in the advanced options, but the cards don’t show up for selection…
You can now select Nocturne from the top of the main menu where you are allowed to auto match. Just select Nocturne, click match and wait.