Based on the selected project type, you will be prompted to select at least 1 asset of that type to anchor your project around.
Primary assets can only be one type of asset for a given project. For a substation project, for example, select 1 or more substations as the primary assets (e.g. can't add transmission lines as a primary asset on a substation project).
Select at least 1 substation as a primary asset
Select at least 1 line as a primary asset
Select at least 1 parcel as a primary asset
As you select primary assets to add to your project setup, they'll be listed at the bottom of step 2 in the flow.
Here's an example of what that looks like:
The next pages will walk through various methods to add primary assets to your project setup: