Firstly, you need to create your material. You do this in "materials" (Ctrl-M). This will bring up the materials list, which shows all the materials you have loaded. You'll probably have none, so all it will show will be one big square button marked "New". Double-click on this button. This brings up the Material Editor. Click the "Textures" button. This will bring up the Surface Texture Editor. In the second entry down (Diffuse), click on the [...] button on the right, which will open the Texture Selector. You can either use one of the loaded textures ("Checks" is the only one there by default), or click "Load Texture" to load your own image.
Phew! I can see why you could get lost doing this...
Once you've loaded the image, it should appear in the list. You'll need to click on it so that it is highlighted, and hit Ok. It should now appear in the box marked Diffuse. Hit Ok again to close the Surface Textures dialog, then Ok again to close the Material editor.
Ok, we're neary there...
Now select the object you want to texture, and click the button with your texture in it, then click Apply.
This is the "Fast Track" to loading a texture, and I haven't shown you how to manipulate the texture etc. But it should at least get you started.
Andy