1. In Edit Town mode, find the Aleister's Elixirs and Sundries (Elixir Consignment Store) in the Community Lots tab.
2. Look for a 30x30 or larger lot to place it on. Before placing the lot, you need to change the lot to a community lot.
3. Change the lot type - Left-click on lot and then click the house/bench button to change lot to community > Lot type: Elixir Consignment Store. Click the checkmark when finish and confirm the change.
4. Place the Aleister's Elixirs and Sundries (Elixir Consignment Store) on the lot you just changed. Select it in the Community lots tab, place copy > drag it to the lot (has a photo of a bench). -- Rotate lot how you see fit and click accept.
Then you're done. It may take a game-day or two to staff the place, like KRae mentioned.
There have been a time or two that I've had to wait a game day or two and then replace the store due to the cash register not working properly. I'm thinking it maybe due to one of the holidays. Leisure day or something like that. - Can't remember exact day. As the staff have the day off and the register is closed.
I made the mistake of trying to place the shop on that day or close to that day and somehow it glitched it. But I waited it out and a couple game days later I just replaced the whole shop.
If you want to replace just the register - Click on the lot, choose Build/Buy mode. Select Community Objects. Under Misc tab look for the Elixir Consignment Store Register.
While I was putting my notes together I noticed you may need to bulldoze another community lot if you're trying to place the shop in Bridgeport. If that's the case all you do is click it and bulldoze the lot you choose and then do step #3.