It is really quite simple, there are going to be three answers you can get Homozygous Dominant (TT or two capitol letters), Heterozygous (Tt one capitol and one lower case, and Homozygous Recessive (tt or two lowercase letters). To find the specific genotype or phenotype, you look at the letters and compare them to the chart. For the punnett square, you use the two parents genotypes, and put one on each of two sides on the square and take one letter from each side of the square and put them together. The probability is just how many of each is that specific phenotype, but you will want to us either ratios or percents. I hope this is helpful.
