To print a document from a SMRT terminal we always use Google Cloud Print.
Like you do on a computer, press the print button in SMRT. Some extra steps are required if this is your first time.
First time ViewSonic VSD231
The ViewSonic VSD231 will need to install Google's app from Google Play. SMRT app will take you to the download page if needed. If you don't have a Google account signed in to this device it will first ask you to create an account or sign in. Select your account carefully. It will be kept on the device and can be used for more than printing. This is required to download the Google Cloud Print app.
First time other devices
SMRT app will open a Google login page. Sign in with an account you only use for printing.
After signing in to an account, all printers that you've used with this account will be listed. No matter if the printer is on the same network or in another building. The print job is sent over internet. Press on the printer you wish to use.
Add new printer
This varies between manufacturers and models. Please look at Google's guide here.
In the top right corner you will se a button labeled "Print". Use this one to start printing. After the print job is sent to the printer you will get back to SMRT app.