how do i start up a subaru dealership?

You don't.  You buy one that already  exists.

you don't        

I wouldn’t bother , they seem determined to lose a bug chunk of their loyal customer base by doing  away with high performance cars and concentrating on run of the mill SUVs all with horrible CVT.

You need a few million in either cash or loans, approval as a franchisee from Subaru (very difficult), a properly zoned property to do business, a building and showroom, a maintenance building, tools and equipment, employees, insurance, a business license from your local government, a tax number. Oh, and you need to buy cars from Subaru to sell in your store. Then you'll need to pay for advertising and marketing and hope that you get customers.

Besides the money, no company is going to give a franchise to someone unless there is demonstrable odds of success .  Sorry - but you need a complete business plan outlining the research done to pick the location, the facility, tools, signage, marketing, staffing, pay, benefits . . . and about a years worth of operating funds on hand.

If you have to ask you don't have the money to do it.

Contact Subaru USA.  You would need millions to buy a franchise, showroom, repair shop, body shop and inventory.