It's a simple task. Use 4 straight lines, one after the other, to connect these nine dots
|connect the nine dots using four straight||lines|
Now, let me show you and example of a failed solution, just to make sure that you get the rules.
In the following picture you see four straight lines, one after the other. It connects 8 dots, but fails to connect to the last dot in the middle of the left side. These four lines probably started at the top left corner, went right to the right upper corner, then down to the lower right corner, then left to the lower left corner, and then diagonal to the upper right corner. But it misses the dot on the middle on the right.
And, again, to make sure you know the rules, another picture. This picture shows an illegal solution. The four lines HAVE to connect to each other and you have to draw them one after the other. Basically you need to put the pen down, and not lift it until you have drawn four straight lines.
In this picture all dots are connected, but the lines aren't. So, once again:
Your job, should you choose to take it, is to put the pencil down, draw four straight lines one after the other, and connect ALL the nine dots.
Go to work now, see if you can solve it.
and when you give up, take a look at the solution.