What planes to you have as your base for your start part?
Also, how are you importing the step files? As imported features
or as a dumb solid. Based on the fact that you have planes out in space
it sounds like you have imported it as features.
Can you edit the features once imported?
Do you know what software exported the step file? Maybe it can be adjusted on that end.
The planes are out in space because that's how the model was created.
After importing the part
Create a User Coordinate System (UCS) at a logical origin point and set the orientation to suit
Save as a parasolid and set the Options to use the new UCS as the Output Coordinate System
Open the parasolid and the UCS will have been adopted as the global default