There are 2 different ways you can do this and my web page ice cream rippling gives the details.
You also need to think about what sauce to ripple the ice cream with. Again, there's so many to choose from. After raspberry sauce (naturally!) my favorites are strawberry, toffee, chocolate and last but not least maple syrup. If you want to make your own sauce try my toffee sauce recipe (see bottom of web page link).
Don't forget, it's still National Ice Cream Month so there's no need to look for an excuse to make your own homemade ice cream - especially if you've never rippled before!