After installing Linnworks Mobile on your device you will be asked how you want to login to Linnworks. There are two types of login. 

Single user device - once logged in, the user will remain being logged in to Linnworks even if the device is turned off or locked. This means you don't need to enter your username and password everytime you need to access the application. This is only really applicable if you are the only user of the device. Only works if you have Screen Lock activated on your device.

Multi user device - assuming the device is shared among different users. For example it is used in the warehouse for counting stock or picking orders. In this case, after each username + password login, the user will be prompted to setup PIN code. In order to login to Linnworks going forward the user can simply use 4 digit PIN code instead of username and password. Linnworks is also locked every time the device's screen locks out or another application is opened. To reactivate the session the user will have to key in the PIN code. This prevents staff in the warehouse using each others' logins, causing the living hell in the audit trails and permissions. 

Remark: If you changed your mind about the login type and want to change it, uninstall the application from your phone and reinstall it again. The Login Type wizard step will appear again.