Where are you supposed to post this picture?

To resize a graphic file, such as a .bmp (ugh) or .jpg or .gif you generally
need to use a graphic editing tool/application.  A good free one is
IrfanView, which can be obtained on line at http://www.irfanview.com. What
you will want to do is to 'resample' the original file to get the requested
72 to 96 dpi range, and then resize it to get the largest edge down to 6
inches if it needs to be resized after that.

If you need help using IrfanView or just need help with the graphic file in
general, I'd recommend asking for assistance in this discussion forum:
http://www.dslreports.com/forum/dimaging
You do not need to create an account there to post, although it does help
people get in contact with you.  Tell them '2kmaro' sent you and I think
you'll get a reasonably warm welcome. The nice thing is that you will also be
able to upload your image file and someone might just do the work for you!