A fruit cake is made from the regular ingredients that a normal cake is made from.
And also the fruit cake is made with fruits and sometimes candies.
Most commonly dried fruit is what fruit cake is made from as well as candied or dried fruit, nuts, and spices, and optionally soaked in spirits.
So you make the cake and then add the fruit in with the cake mix which is how I've always made the fruit cake with.
Mix up the cake batter and then add in either dried fruit or even fresh fruit.
I prefer to use fresh fruit when making a fruit cake but some people prefer to use dried fruits to make their fruit cakes.