How do I make and set a Ortho Matrix in OpenGL ES?

So I’m making a 3d game in Android, and I wanna overlay buttons to move the player.

My questions are:

1)How do I get the current matrix as a float array/buffer in OpenGL ES for Android (4.0).

2)How do I set said matrix into a Ortho Matrix?

3)How do I make my current matrix said Ortho matrix?

If this isn’t clear, or there isn’t enough info please post saying so.