A graph is on a grid known as the "coordinate plane." We locate and name points on the graph as (x,y) meaning that we count x units from zero on the x-axis (going across) and y units up or down.
If you have a line drawn on a graph, find 2 places where the line goes directly through a "cross" and find the coordinates (x,y) of those points. You can then find the slope by finding the difference between them.
As another tutor said, the slope is "rise over run" so it is the opposite of how we name points. You can find slope on a graph by starting from one point on a line and counting units up/down then left/right to get to another point on the line.
You can also find slope using the coordinates of two points, (x1, y1) and (x2,y2). The slope is the difference of the y's over the difference of the x's, that is:
y2 - y1
x2 - x1
The slope is written as a fraction or integer.
I hope this helps you!