This is a screenshot of a drawing from youtube and the designer was using Illustrator.
GDSE is not a tutorial on request site, but since you are obviously new to Illustrator, I will attempt to give you an idea on how you might proceed. The following is a simple method that could be used in Illustrator CC, not sure about CS6 since I no longer have a copy I can check to see if it has corner widget functionality. However there are many ways this could be done even if you are using an old version of Illustrator*. I'll let you decide if you think it's worth the upgrade.
You can begin by using the Pen tool to create straight sided shapes. Holding down Shift as you use the Pen tool constrains the angles. Also, switching on Smart Guides will also help you line things up.
Next, select the shapes using the Direct Selection tool (A). And select each corner widget in turn, and bend as required by clicking and dragging the corner widget.
*In older versions of Illustrator without the corner widget functionality, you will probably need to add additional curve anchor points and bend the Béziers manually.
Other possibilities include using rounded rectangles and the pathfinder Minus Front/Unite, or Shape Builder tool to combine shapes.
Here's an example using a regular rectangle, and some rounded rectangles and the Shape Builder tool