This is a classic Punnett square question. The hardest part of setting up this problem is determining the genotypes of the parents. All of the needed information to solve the problem is there if we take the time to digest the problem. The first information given to us is that yellow is dominant to green. That means that if one allele in the genotype contains yellow, then the plant will have yellow peas.
The next information given to us is that the first parent is heterozygous yellow. Heterozygous indicates that this parent has both alleles for the gene. Just as a reminder, homozygous genes have the same allele, but does not indicate if the alleles are dominant or recessive.
The next parent is a green pea plant. Notice that they do not tell us if it is heterozygous or homozygous. For a student who is new to the material, this may seem confusing; however, the question has stated that yellow is dominant to green. This means that, in a green pea plant, no dominant alleles are present and must be heterozygous recessive.
To set up the Punnett square we have to define our alleles. Lets have Y be the dominant yellow allele and g be the recessive green allele. From the information that we have established above, the parents genotypes are Yg and gg.
The Punnett square involves drawing a two by two box. Due to the lack of drawing tools I will do my best to explain how to set it up with words. There are plenty of videos out there that cover how to properly set up the square. The first parent's alleles will be on top of the box with one letter in each column. The other parent's alleles will be placed to the left side of the box with one letter in each row. Fill in each row with the letter that is to the left of it and fill in each column with the letter on top of it. Each box within the square represents 25% of your population. If you have any questions regarding the information above or my wording was confusing, let me know and I will be happy to help!
I hope this helps!
Quick disclaimer: I am quite new to this platform and am not used to how much information I should be providing to the students. If anyone has constructive feedback on how I can improve my answer without giving away the actual answer, please let me know!