The word "us" here refers to God. God was saying what he intended to do. The pronoun "us" is plural. Possible reasons for the plural use are 1) the plural form suggests that God is discussing something with the angels that make up his heavenly court or 2) the plural form foreshadows the later New Testament implications that God exists in the form of the Holy Trinity. Some translate it as "Let me make" or "I will make." If you do this, consider adding a footnote to say that the word is plural.