Select the character mesh in the Outliner, now head to Object Porperties and set both X and Y location to 0
Last but not least get sure that the Z location (height) is right to, so the chars feet touch the floor grid, if not move the char up or down the Z Axis with 1 unit snapping increments.
You might also afterwards want to change the meshes point of Origin to the 3D cursor, if it isn’t there already ( origin should be at the bottom middle of the feet/legs)
To do so select your mesh and click on Object > Set Origin > Origin to 3D cursor.
When you export it, I recommend you make sure the origin of your .obj file is at X: 0 and Z:0 to ensure that it pastes into blender at the center of the file.
To fix it:
Object > Set Origin > Origin to Geometry
This allows your Origin to be selected to the Object
Or you can do
Object > Set Origin > Geometry to Origin
This allows your Object to be teleported to your Origin which is the circle in the center of the file.
If you’re still confused here’s a tiny video that shows ya what to do.