One must be of legal age to enter into a contract.
If you enter into something such as an agreement, discussion, or relationship, you become involved in it. You can also say that two people enter into something. I have not entered into any financial agreements with them The United States and Canada may enter into an agreement that would allow easier access to jobs across the border No correspondence will be entered into
{f} go into; take part in; get involved in something in an active manner; sign up for
If one thing enters into another, it is a factor in it. There were also other factors that entered into the orchestration