During the match, when it's time to take your shot, you can tap the icon of your Club on the bottom right of the screen to switch Clubs. 

Note: Make sure you have selected preferred Clubs in your Bag in advance. 

See FAQ - How to select Clubs for a match?

1. Click the Golf Bag icon on the main screen to see your Clubs
2. Select the Club you want to put in your bag and tap "USE"
3. If the slots are full, select the Club in your bag you want to be replaced with the Club you chose