Since foundation walls bear the weight of exterior walls above them, you need to insert footings beneath the foundation walls to transfer support for the vertical load.
Strip footings are easy to insert — just click on a wall and a footing is automatically inserted underneath the wall.
To insert strip footings under walls:
Select Insert > Footings > Strip Footings Attached to Walls, or click the Footings button on the Building toolbar and select Strip Footings Attached to Walls.
In the catalog panel, select the footing you want to insert. Typically you would choose one that is wider than the wall you are attaching it to.
Click on the wall you want to attach the footing to. The footing is inserted automatically. In plan view, strip footings are usually shown using a dashed line.
Continue inserting footings underneath each exterior foundation wall.
Right-click and select Finish.