If you are graphing on a number line, then you would plot an open circle at 4 and shade to the left of the open circle. The open circle tells the reader "do not include this point as part of the solution set". The shaded region is the solution set.
If you are graphing on the xy coordinate axis system, then you'll graph a vertical line through 4 on the x axis. This vertical line is made to be dotted or dashed to tell the reader not to include any point on the vertical line. Shade to the left of this vertical dashed/dotted line to represent the set of all solution points. These points will have x coordinates less than 4. The y coordinate can be any point you want. Eg: (3,5) and (2,7) are two such solutions.