I am a new user of mach3 and am haveing a terrible time Jogging. How can I slow down the jog speed, It is jumping all over the place. Any help would be appreciated.

I do not know what version of Mach you are using, but I believe at least on all of them, if you goto the Diagnostics screen, it will have the jog speed listed as a percentage (of your max speed). you can change this by either clicking the buttons with the mouse or hitting the "[" key.
The "]" will increase the jog speed.

on a side note, holding the SHIFT key while jogging will override to full jog speed. Make sure you shift key is not stuck (has happend to me in the past-- got another keyboard!!).

in Mach3 Press the "Tab" key and you will get a slide out with the SLOW JOG DRO with arrows to make it higher or lower.