I hope what I say here is understandable...if it isn't, I am sorry and I apologize.
Here's an example.
Marie is a generous woman.
First, you look at the noun(s). There might be more than one, but look specifically for the one that is being described by an adjective.
Here are some things to note. Nouns are people, places, things, or ideas. Proper nouns are like names of people, places, pets, and whatever has a name. Common nouns are everything else without a name. They're not specific, basically.
In this case, the nouns would be "woman" and "Marie." But the noun being described is "woman" since "woman" is described as generous.
You would then underline the noun and circle its adjective.
Now, you need to determine which ones are singular and which ones are plural. We would look to the noun being described.
In the example sentence, the noun "woman" is singular, meaning that it's only one thing/object/person. Plural is more than one.
So since woman is singular, its adjective also has to be singular.
This is similar to determining the gender of the adjective. We look at the noun.
Women are feminine. Thus, the adjectives to the word "woman" or anything related to women have to be feminine. Although, there are cases where this rule doesn't apply, but let's not worry about that right now.
So now, for the example sentence, we'd have to checkmark the column of S and F.
Hope this helps. If it's confusing, sorry! Maybe the information in the bottom box of your homework could explain more than what I did.