Hi Harriet:

First, if you are under 30, you may find it impossible to orgasm vaginally.  For some reason, women become more orgasmic in their 30s and even 40s. 

Second, its difficult to give yourself a vaginal orgasm because you would need to stimulate your G-spot. Some women, particularly young women, cannot find it.  That spot, when stimulated, gives vaginal orgasms.  Women often use a vibrator or dildo to rub that spot, as it may be difficult to get your finger(s) in the 1 to 2 inches needed to find it.  Its 1 to 2 inches inside your vagina, and on the front side.  It will feel harder as you rub the area, and you will notice sexual arousal when you find it.  A vibrator is the easiest way to give yourself a vaginal orgasm, as the vibration covers much of your vagina and more likely reaches your G-spot.