You can change clubs by pressing up or down. The "W" clubs are wooden clubs and they hit the farthest, with W1 being the longest-range club and W3 and 4 being increasingly shorter. After wooden clubs come the "I" or iron clubs, which all hit for a shorter distance than the W clubs. The PW(pitching wedge) and SW(sand wedge) are wedge clubs which hit even shorter, but as a bonus lob the ball into greater heights, and are particularly useful for getting the ball near the hole with precision, or getting them out of sand bunkers. Lastly there is the PT(putter), the weakest club, which does not fling the ball into the air, but rather is used for delicate pushing of the ball into the hole.
The swing sequence consists of three presses of the A button. Once to begin the swing, second time at the swing's zenith(the left-most side of the field) for the most power(or less, as desired), and the third time around the white area to hit it and send the ball flying. If you somehow miss the white area, don't worry, it is still a hit, although hitting left or right relative to the white area determines the ball's trajectory. Hitting left of the area results in a slice(the ball leans right), while hitting the right of the area is a hook(it leans left). Here's a
diagram. The putter plays slightly differently: It has the start and power press, but not a directional press or a white area, because it always shoots straight.
When you're near the hole, the screen turns into the "putting area" where the only club you can use is the putter. The yellow arrows represent the slope of the area, and it will slightly affect your ball's trajectory. As a general rule it is always a good idea to underpower rather than overpower the putter.
There are 18 courses in total and I hope you won't find yourself lost in the game. For the best scores the courses have a "par" count(which is a maximum number of hits designated for every course), although the game does not punish you or give you special credentials for not meeting the par number. You can just clear courses in however many swings you like. Have fun!