Has_secure_password rails change password_digest to password

Hello im using my rails app to access an existing project with a database that cannot be changed. So my question is how can i create a session using Bcrypt without the need of haveing the column password_digest in my DB?, I already have stored in my DB the password in the column password.

Here is my code

def create
     user = User.find_by(email: params[:session][:email].downcase)
     # user.update_attribute(:last_login, DateTime.now)
    if user && user.authenticate(params[:session][:password])
      log_in user

      flash[:success] = "Bienvenido de nuevo #{current_user.name.upcase}"
      redirect_to user
    else
      flash[:danger] = 'Email invalido/Contrasena incorrecta' # Not quite right!
      render 'new'
    end

  end