Imagine that you are studying two parents who are considering having children. one parent has the genotype i and the other has the genotype i. create a punnett square to calculate the possible genotypes of their children.

I found the exercise on the internet and this is how the genotypes should look like (these genotypes are ABO blood system genotypes):
i and i

Attached is a Punnett square that represents the crossing between both parents and the possible genotypes of their children.
You can do a Punnett square by inserting on both entries of the table the alleles that correspond to each parent, being each table entry a parent genotype (as shown in the table/Punnett square below). Then, join the alleles from each parent as they appear related to the central squares. The formed genotypes are then the possible genotypes of their children - , i, i, and ii