following the included installation instructions should be sufficient, however if you are inexperienced with configuring php programs, i would recommend starting with something easier, or if you need php nuke installed right away, sign up with a webhost that offers a Cpanel control panel, with fantastico, because cpanel offers a one click install of phpnuke and fantastico offers a one click install of phpnuke along with about 15 other popular open source scripts.
http://www.pr-design.biz is a host that offers both. maybe check it out.