Yes, you sum up the drag from all the different components, such as the wing, tail, and fuselage. Also toss in induced drag, and guess at the amount of cooling and interference between the different components like the wing to fuselage junction.

On paper, it is just a guess. It's not till the airplane is fully tested that better number emerge.

On the origninal design it was thought that it's total drag area would be 0.31 sq. ft. But as the design evolved (retractable gear were eliminated), the drag area went up.

A more interesting question might be why did it crash at the end of the first flight? I believe it was due to vertical stabilizer being mounted inverted under the fuselage to protect the propeller (it was a pusher design). At some angles of attack, I believe that the rudder action would reverse, so when the pilot pushed left, the airplane would respond to the right. The end of the first flight ended with the plane snapping over and crashing inverted killing the pilot.