I usually create maps for a specific final dimension size. Since this map is for a tutorial, I created an 8.5 x 11 inch map at 100 pixels per inch for ease...
Step One: Once the page is setup, I begin creating a coastline shape, using the freehand tool from edge to edge. Once I reach an edge, with the freehand drawing tool still selected, I click and hold the Alt key, which forces the freehand line into a straight line, which drag to the corner of the page, release the Alt Key, the press the Alt Key again, and continue along the edge to the next corner, eventually closing the shape from the starting point.
The default color is black, but I want a more subtle shade of green. I click the color menu at the bottom of the screen and choose the color I want.
The first image below shows the green shape I created...
Step Two: I want to create a river extending from the right side of the map reaching the coast. This requires drawing both sides of the river narrowing to a point at the source and widening out at the mouth.
Because it is difficult to maintain the proper distance from river bank to river bank, once I complete the shape, with it selected I click the "point mover" tool located just beneath the freehand tool on the left side of the screen. Its a black line with some "bezier curves" handles in red. I zoom in close to the river and begin altering its shape to best fit my needs.
The second image shows the closed shape in the default color black.
Step Three: I create a fork in the river, by freehand drawing a tributary. Using the same techniques as step two. The difference is the use of the Arrange/Combine/Add from the main menu at the top of the screen. This combines the two river objects into a single object.
The third image shows the combined rivers.
Step Four: With the combined rivers object selected, I click and hold the Shift key, which allows me select additional objects with the river object, in this case the background regional map shape. Once both objects are selected use Arrange/Combine/Subtract.
Its important to note that the object located above the two selected objects is what becomes subtracted. If you placed the river object beneath the continent shape, the land get subtracted instead. Make sure the object you want to subtract away is above the other object.
The fourth image shows the subtracted river from the land shape.
Step Five: Although not always necessary, I wanted to create a plateau where I plan to place a mountain range. So I draw a shape straight at the edges as in how the land shape was originally created, then a freehand shape skirting the rivers to create a canyon effect around them.
Image five, shows the closed plateau object.