Can someone please help me with this, or explain it to me?

Answer:
Argentina: argentino, argentina, argentinos, argentinas
Bolivia: boliviano, boliviana, bolivianos,
I only did the first two but I explained it.
Its how you call the people from that country. So Masculino Singular means: Singular masculine/ One guy. Femenino Singular means: Singular feminine/ One girl. Get it?