1) you will need a photo editing programme to reduce the size of your photos before you post them to the web.
GIMP is free and has documentation which teaches you how to resize and edit photos.
Download:
http://www.gimp.org/downloads/
Tutorials:
http://www.gimp.org/tutorials/
I normally resize my photos to 800x600 pixels or 1024x768 pixels for landscape photos and the 600x800 or 768x1024 for potrait.
There is normally an option to maintain aspect ratio, ie the dimensions of the photo was taken in the camera, which you should keep on. So if you took a photo with a wider aspect ratio (think more rectangular) then you will maintain a width of 800 pixels while the height will automatically be calculated and keep the same viewing perspective instead of forcing the photo to look wide or narrow.
2) to upload to the web, you have a couple of options. You can upload the images to this website to share with others (as you have attempted in the past), or you use a free photo sharing service like Flicker, Piscasa, Photobucket or Imageshack to host the files which you will link to.
If you choose to use the website, then you can only use the photos on the website (simply speaking). If you use a photo hosting service, then you can share your photos on social media, on forums, etc.
Here is a 1 page primer for you:
http://www.digicamhelp.com/processing-p ... ng-photos/
I hope this helps