The time is drawn on the x axis. The magnitude of velocity is drawn on the y axis. We assume that the speed is in the same direction.
Then at each point of time t = 0 sec, 1 sec, 2 sec, etc. we find out the speed. A point is marked with the ordinate height = speed.
If the time range is a large one, choose the scale on the axis on the graph, such that the width of the graph paper is sufficient for the range of time duration. so scale = T seconds/ centimeter.
if the speed range is large or too small, select the scale such that the range is with in the height of graph paper. so scale = V m/sec / centimeter.
If the velocity is always positive, then, draw graph only in the first quadrant. If it is also negative, then draw the 1st and 4th quadrants only.