If I understood you, you are going to create a fresh custom page in Aurena. If so, it seems like you have not added the list to the page all elements section first.
In the Page Designer, if you need to add new content to the page, first you need to configure those elements using the ALL ELEMENTS section in the page designer.
In your case please go to ALL ELEMENTS > List.
And then click on the ‘+’ button appears in the right to add a new list.
In the new element dialog appeared, add the Entity and other details.
Then under the new list you created, you will be able to add content and other configurations for that.
Finally, you can add it to the active page content by following the last two steps you attempted earlier. Now, you will be able to select the list you just configured from the dropdown.
Set the Datasource and other configs to the list accordingly.
additionally refer this for Importing & Exporting of Configurations thorough environments Importing & Exporting of Configurations (ifs.com) ( As you have said that you have already created the custom objects in IEE)