Plug in x1, y1 and x2, y2 using your ordered pairs, (6,3); (4,8). It makes it easier to label your ordered pairs so you don't get confused. (X1= 6; Y1=3 || X2=4; Y2=8)
m=8-3/4-6 Subtract 8 from 3, which would be 5 (x). Subtract 4 from 6, which would be -2(y). Now, put them together to get your slope. m=5/-2.