Trust your instincts!
Although this recipe may seem unusual, using ground almonds and polenta instead of flour, there's no need to be apprehensive! In fact, the process you need to follow is the same as any other cake you'd make using the creaming method!
You still start the process by incorporating as much air as you can into your mixture, creaming the butter and sugar together and beating in the eggs pretty vigorously.
Likewise, you'll still want to fold the dry ingredients into the batter until just combined, rather than beating with any sort of force. In cakes containing flour, we do this partly to prevent excessive amounts of gluten from building up in the batter, which can make a cake turn out slightly dense and gluey, rather than light and fluffy.
In this recipe, however, there's no gluten involved, so why do we still need to be careful? Well, as you beat, fold and generally interfere with the ground almonds, they'll start to release oils, which in moderation can provide a lovely moist texture in your final bake, but in excessive amounts can turn your light, airy batter into more of a butter!