Cant login using IP address

I am fairly new to wordpress. I have about 6-7 sites already done using wordpress and they are doing pretty good. The problem I’m having right now is that I am wanting to do a wp site for a customer. Her domain is currently live with another host and I want to have her new wp site ready before re-pointing her dns to my server. I installed wp using fantastico deluxe, but cannot access the admin login using the ip. What can i do to access, install a theme, and build the site prior to re-pointing the domain? I went to https://00.00.00ip address/wp-admin but only get a 404.