I purchased numbers on my iPad & also bought an iPhone 5. How do I also get Numbers on my iPhone 5?

As you purchased Numbers on the iPad, you can install Numbers on your iPhone for free. See > http://support.apple.com/kb/HT2519

Assuming you are using the same Apple ID on both (you should be!) then open the Apple Store app on you phone, and tap "Updates". You should see a banner across the top that says "Purchased". Tap that, and you can select the Numbers app to download. You can also sync your iPad to iTunes, then sync your phone, choosing the apps you want in each case.