Samsung SmartThings users access their devices from two unique apps:
- SmartThings - used for the initial setup, removing or adding hubs, and managing IoT devices
- HomePass - Used to manage the WiFi network (Please note that if you are located in Canada, you need to use "Plume for SmartThings Wifi").
Step 1
Ensure your phone is signed in to the Samsung account and is connected to the Wi-Fi hub. You can read the instructions here.
Step 2
Upon opening the Plume App, you will see the following screen. Where you will select the, I'm using SmartThings Wifi button to log in to your SmartThings account. 
If this button is not visible, there are two possible reasons:
- Double-check if the SmartThings app is installed on your phone, and confirm that you are logged in.
- SmartThings Wifi is only supported in North America.
Step 3
You will be prompted to log in with your Samsung account. This is not your Plume credentials. SmartThings users do not have unique Plume credentials.
Step 4
If there are no SmartThings Wifi Hubs added to your SmartThings account you will have to open SmartThings application and add Hubs.