There certainly is a way to do so on the iPhone -- in fact there are two -- and please don't call me Shirley. :-)

I'm glad to hear that you have your computer and iPhone synchronizing on the address book / contact information too. It's pretty darn important, particularly when you get to the size address book I have (over 550 entries). Losing it and having to rebuild from scratch? No thanks!

There are actually a lot of ways you can get to the Contacts program on your iPhone, including the actual Contacts app itself, but my druthers is to work within the Phone app since that's usually why I am adding someone while on my cell, to remember their telephone number.

Here's how I add a contact to my own iPhone address book...

First off, I've pinned my Phone app to the lower bar where it's always accessible, as you can see:

A tap on that and I'm ready to make a phone call:

Look closely at the bottom of the screen, however, and you'll see a set of icons. Left to right, they're Favorites, Recents, Contacts, Keypad (what we're looking at) and Voicemail.

Tap on "Contacts" and you'll see your contacts, if any:

Most important, however, is the "+" button on the top right. See it, just under my battery indicator? Tap on it and...

There ya go. Enter their name, numbers, email address, tweak the ringtone or text tone for this particular person, add a photo if you're so inclined, and -- most importantly! -- tap on "Done" on the top right and you've just added someone to your iPhone contact address book. Congrats!