How can I straighten out my dishwasher?
Usually they are fasted to your cabinet at two screw tabs along the upper front edge of the dishwasher. Open the door and look along there, as your first step would be to check/remove the mounting screws.

It is likely that the mounting tabs have been bent, causing the unit to sit in a non-level position. It's important that you get it back level or it may not operate properly and could leak. Once you remove the screws you should be able to carefully pull the unit out a bit to straighten the tabs.
There is a chance that you may also be fighting copper water supply tubing that has been distorted/bent/kinked when the unit moved. If this is the case, you will need to shut off and disconnect the water supply, power, and drain lines and pull the entire unit out to inspect and repair as needed.