If you upload your model facing the wrong way, you can easily rotate it around under 3D Settings.
Orientation (Straighten your model)
You can change your model orientation by 90° increments around the x-, y-, or z-axis.
Under the 3D Settings page for your model, click the first tab (the gear icon below) to access your Scene settings.
Select Show advanced rotation to fine tune any axis at any angle. Typically, you want the top of your model or scene to match the blue "Up-Axis" of the coordinate system. This is usually the solution to upside down or sideways models.