Well, I resize pictures by using the program called 'Paint', I'm sure you have it. If you have a windows system that is

.
Now listen up, even if your not ElvisHendrx0, lol.
To resize a picture:
_____________________________________________________________________________
1) Open your picture in Paint(I hope you know how to do that).
_____________________________________________________________________________
2) Go to 'Image' on the menus above and click 'Sketch/Skew':

_____________________________________________________________________________
3) This window should pop up:

_____________________________________________________________________________
4) Now it depends on what numbers you type on the highlighted areas that will make your picture bigger or smaller:

_____________________________________________________________________________
The smaller the numbers, the smaller the picture. The bigger the numbers, the bigger the picture. Now everything you type is percent-based, so how bigger you want it by percent is generally what your typing in.
Note: Make sure that the numbers you type in are completely the same as the other number. Look at the following examples to see what happens if you don't:

-----------------------------

Will form this picture---V-----------------------------------------Will form this picture---V

--------------------

In this example, I typed in '50' and '50', which makes the height and width of my picture 50% smaller. If I type in '150' and '150', it would make my picture 50% bigger. Now on the other image, see how its all distorted? I typed in '50' and '140' to generally make the picture 50% smaller in width and 40% bigger in height.
So, I hope this helps