On the computer, you can login, select an asset by clicking the asset ID and then on the right top side of the screen click check in or check out.
On your smartphone. follow these steps:
Start the app
Scan the barcode on the item or enter text to search
You will see one or more assets on the list
At the bottom right is a button called 'Check In' or 'Check Out'
click the button and asset will be Checked in/out
View that has now been changed using the mobile app or computer