how can i tell on a position-time graph if it is speed or acceleration

You didn't say what "it" is.On a position/time graph, the slope of the graph at any point is the speed at that time.If you want acceleration, then what you'd have to do is to measure the slope at every point on the position/time graph, then use that information to draw a speed/time graph.  The slope at every point on the speed/time graph is the acceleration at that time.