Is there a way to add more resolution to a terrain or do I need to start with a smaller patch and dupe them?

Also, can I join these smaller one into a larger one? I can't get smooth hills right now.

Shift + Control + Plus will increase patch columns.
Control + Plus will increase patch rows.

You can only "join", or merge, equal density patches when their vertices line up and the resulting patch will be no more than 16x16. Select two patches and hit the "W" key.

To weld or line up vertices, select your patches, hit "V", drag a box around the vertices that you want to line up, then hit "W".

Tip: When you are welding vertices, the vertices on the patch that you select first will become the target. All selected vertices will be welded to the target vertice.

Thanks for the reply. I get it now. I made my terrain half the size, duped it 3 times and made sure they were perfectly lined up. Now when I paint height, it's seamless from patch to patch.