Place AR Object next to Marker

Hello,

i have to make an Android build for AR in a university project. We have to place an object when the image marker got identified but i am wondering how i can choose the position of the object in relation to the marker. How can i fix this position in the coordinate system? Is in Unity an option to see where the marker will be and where the object is placed so that i can adjust the position how it needs to be?

Hope you understand my question :D

thanks alot xx