Q: How do I send text using iPad?

Despite the fact the iPad is cellular capable, it is not capable natively to send SMS, as the device does not have a phone number. The number it has is just an account number for the company to use to bill your usage. The cellular capability of the iPad is for data purposes only.

As indicated by others, the type of application you use in the App Store is your decision. There are a number of them, however most require the recipient to also have the same application. That is one of the drawbacks, because the iPad again, is not a phone. As far as iMessage is concerned, the sending and receiving of those are for iOS devices only. You would only be able to iMessage between other iOS device users. You would set up iMessage in Settings, an it uses your Apple ID email address to send the messages. You would need to know who actually has iOS devices before you attempted to send an iMessage to your friends/associates.

To address your final comment about "user friendly", "easy to use", the devices are. The iPad has never been advertised as a texting device, just that is has the capability to use iMessage. There is nothing for them to "get back on tract", since the iPad performs as most tablets do. And as others have said, it does have the ability to send an SMS, if you also have an iPhone to use.