To add or change custom field properties of the asset:
Go to Dashboard -> Asset & PPM or More -> Asset & PPM
Asset Management Dashboard with all menu options on the left side will be displayed. Click on Asset Icon to go to Asset UI.
On click of Asset, you will see the list of existing Asset. You can also filter the asset by selecting from Search/drop-down at top left of the UI
Click on the Asset Name Link. You will see the UI with Asset details.
Add the details as per your need and Save.