I'd very strictly an amateur with photography, but I have an Olympus D460Zoom that came with Camedia Master 1.2. I've started taking all my pictures with next to the highest resolution, then after I load them onto the computer, I open them with Camedia Master, click on "Image" in the toolbar, then "Instant Fix" which frequently makes them lighter and look a little better, and save that version. I right click on a picture, then click on "Properties" to see what size it shows in width and height, as well as the file size. Then with the picture open in Camedia Master, I click on "Image" again in the toolbar, then click on "Resize" and adjust downward in size.
Now since I don't really know what I'm doing, and never know exactly what the file size will be with different widths and heights, I sometimes only reduce it a little bit, the check the "Properties" again to see what the file size is, and maybe have to repeat the process.
Another thing I do, is to save the original picture at the higher resolution, after using "Instant Fix", then "Copy" that picture into a different folder and use the copy to adjust the size before posting it on this forum or sending it via e-mail to anyone. That way if I mess it up, I can always delete it and start over with another "copy".
Now we have a bunch of real photographers as members on this forum who might tell you an easier, simpler, or better way to do it, but it works for me, and of course, I don't know what differences there may be in my version of Camedia Master and yours.