The User Preferences
You MUST go to the [addons] tab of the user preferences after installing True-Assets v4.0. Search for True-Assets and then from there we will address the steps that must be taken to get the AmbientCG library to appear in the Asset-Browser.
Open the Blender user preferences> Addons > True-Assets (If you have not installed yet, go to HERE)
Set a download location for the AmbientCG library to store assets you have used (shown in the red box in image above)
Open the True-Assets Directory location (Shown in yellow box) using the folder button to the right. This will open a file-viewer.
Either find a location that you wish for your True-Assets libraries to store if you have NOT already done so. OR, if you have already chosen one, just click [OKAY] in that file-viewer pop-up, to refresh True-assets to build the AmbientCG library.
Save the user preferences (Even if you have auto-save enabled) to ensure that the directories you have set, are set-up within Blender's file path menu.
You need to follow these steps as shown, whether this is the first time you have installed True-Assets, or are an existing user of True-Assets. The Libraries will not update without a prompt from the user.
The Asset Browser
Now you have completed the steps above, you can head to the Asset-Browser of Blender. Once there, you'll see the drop downs for all the True-Asset's libraries, now including the AmbientCG library.
Once you see this Library in the drop down, select it and follow the Steps on the next article