Something like that is going to produce insane amounts of drag, and will be hard to fly into orbit. I once had to lift something that looked similar that was part of my space station which couldn't fit in a fairing and couldn't be broken down into smaller parts (without using KIS/KAS mods), so I had to fly it in a very different manner than usual. With that much drag, you will have to go straight up for quite a while, almost to 20-30km or higher. Be sure you can stay stable during this ascent period because even a very low angle of attack can likely cause you to spin. Once the atmosphere has thinned out, you can start pitching over to the horizon, but be sure you still do this slowly and gently. Of course this kind of ascent is very inefficient use of fuel, so you'll need more than usual to reach orbit, but you might not have any other choice. Press F12 in-game to see drag-related arrows on the craft, that'll help you with the flight (the red lines are the drag, don't let them get too far away from the center of mass). Alternatively, you can redesign your lifter to be much less draggy, but that payload will still need to be nursed into orbit.