Q:

How to resize a photo?

I know this is really a noob question, but it has always confused me. If something says "Images must be 210 px high and up to 375 px wide." how do I do that? I assume one uses a program to do it, but which program? Or maybe just cropping?
I know this is similiar to this question
but I am not a programmer. The difference between that question and mine in that I need the answer in not-a-programmer language.

A:

Use a copy of your file, do not resize your original photo.
You can use this free program: http://www.gimp.org/
Using Gimp:

Open your file.
Use the rectangle select tool. (Define some initial dimensions to set the  proportion you need) Move it, scale if from the corners to mantain the proportion and frame your image.
Menu > Image > Crop to selection.
Now resample. Menu Image > Scale Image. (Use "Cubic" on the quality interpolation section)
Apply a slight sharpen. Menu > Filters > Enhance > Sharpen.

Using Photoshop
(You could use a program like photoshop, but do not spend on a trivial task like this one)

Open your file
Touch the select tool. Define your proportion.
Define on your image the area you like. Scale it and frame it.
Right Click on it. Crop.
Now Resample. Menu > Image > Size. Use the Bicubic or Bicubic Sharper.

