Adding data to the attribute table can be done in 2 ways: from a new attribute table or from a selection.

From a new attribute table

Opening the attribute table

To open a new attribute table go to Windows and find the Attribute table.

Open

Adding data to the attribute table

Select the type of data to add to the Attribute table.

you can add assets to the data type as shown in Attribute table: how to collect data | Add more items to the attribute table

Open

From a selection

Use the box selection tool to create a selection.

Optionally add additional items to the selections by clicking the items in the inspector.

From the selection menu in the top left you can open the Attribute table with the current selection.

Add more items to the attribute table

Select the data type you wish to add to.

Search and select the asset you wish to add and click the + button.

Export the attribute table