To have Salestrail running in the background, you simply open the app, then go back to Homescreen without terminating it. This indicates Salestrail is in the background:
Another thing is the Background App Refresh. It is an option that allows your apps to check for new information in the background in an intelligent and controlled manner. We highly recommend you have this option turned on for Salestrail so the app can work at its best. You can follow the instructions below:
Go to General in Settings on your iPhone.
Go to Background App Refresh.
Make sure Background App Refresh is turned ON (green) for Salestrail.