To put text on a path, you first need a path, obviously. Choose the Pen tool, shape tool, or line tool. Next go to the options bar and make sure the "paths" option is active, then create an open or closed path.
Once your path is created, switch to the horizontal type tool. Bring your cursor close to the path, and your cursor will change slightly, and the status bar will change to say, "Click to create type on a path." Click, then type... that's all there is to it! Well, you do have to click the commit button to accept the text.
If you have created a closed shape, you can also have your type wrap inside the shape to conform to its path. The process is essentially the same as creating type on a path but instead of clicking the cursor on the outside of the path, you will move the cursor inside the path and click when it changes to an I-beam with a dotted circle around it.
All of the type tools work with type on a path or type in a shape. You text is fully editable and though it may appear jagged on-screen, it will print just fine. To edit your text, double click the T icon for the type layer in the layers palette and use any of the editing functions in the option bar, character palette or paragraph palette. You can even warp text on a path or in a shape, but both the type and the path will be warped.