Hey there! I'm happy to help!
When it says f(1), that simply means to look for the x-coordinate 1 and then see what y-value of the function.
If we go to the x-value of 1 and look up a bit, we see where the function is at 1, it is at the y-value of 1!
Therefore, f(1)=1.
Using this, we can see that f(7) is 5, f(0)=2, etc.
Have a wonderful day!