starting openoffice.org portable

Can anyone help me? How do I start openoffice.org portable step by step? I brought a 512MB USB flash drive to install it. I have a Windows XP so when I plug my USB in, it said my USB was installed. Now when I went to click Download Openoffice.orq Portable it took me to a site where I had to choose a mirror. Is this correct and which mirror do I pick? When I pick the mirror, do I save it or run it? Where do I go from here? Thanks for anyone who helps!