how to aim with left thumbstick?

Hello

I am making a fixed camera top down shooter in which i wish to have the right thumbstick controlling all the characters movement (up, down, left, right) I would like to have the rightstick control the characters aim (up, down, left, right). Can someone give me an idea on where i should start please? I have set up the movement but i am struggling with the aim and how to make it independant of the character direction?

Thankyou