A good way to start is to bully congress into irrelevancy. If that sounds familiar that's because it's already been done. Then you shoehorn your cherry-picked supreme court justices into the highest court in the land so you can do anything you want with impunity and without all that pesky advise and consent that shows you down. Then, with all your attention on foreign policy, you set your sights on the malignment of alliances so you can blame them for why they no longer have your military support ~ which allows you to pave the way for Russia to expand it's influence and military power and thus once again become a world power with whom share a common interest.
Multi-tasking all the while on the domestic front, you proceed to fuel culture wars to create a domestic enemy within that you can assign blame for all the problems that cause the downfall of their lot in life. Again with the multi-tasking, you use your new found impunity to guarantee that your financial donors are well funded and appropriately "appreciative" for their new found wealth and thus insure their continued financial support.
Moving on, it will be necessary to keep the world in a state of flux, uncertainly, confusion and fear so they become frozen into immobility. The gravy on that train will be a decline in their economy from lack of secure trade agreements that you systematically and with malicious intent destroyed ~ and have, by extension, created an atmosphere of unrest and public dissent toward their own leaders.
Also, it always helps to have a war on the drawing board ~ just to add to the confusion both abroad and at home.