Sideways Text

Hey

Try typing your word as normal:

Next select: Effects> Distort and Transform> Transform

Then set your Rotation point from the top left and the Angle to 270:

Hope this helps,

Sim

If you are having a problem with your shape rotating, but the text remaining upright, try using the Rotate tool from the toolbar instead of the rotate arrow that appears when you hover over the shape. 

"...like you had to turn the paper sideways to read it."

If you want to set up your document like a letter sized sheet is rotated after you've already started, you can change the orientation in the Properties panel by clicking Edit Artboards and to the right of Preset, change portrait to landscape by clicking on the icon.

"...like you had to turn the paper sideways to read it"

Type out your text ( just as Monika has explained ) > rotate 90 degrees + or - depending on which side of the paper you want it.

Just create it upwards and then rotate it?