Simply, you do not.
To get logged in to the Apple watch app you need to login to Salesbox on you iPhone first. After that you will be automatically logged in to Salesbox on your Apple watch.
The first time you login Salesbox will sync information to the watch. While the sync is active, do not actively use any other apps on your watch since that will paus the sync process. If you still do the sync will restart when you open the Salesbox app again.