Do you have Administrator rights on your PC? You need Administrator rights to
install software. Google for how to get them.
The steps are
1. Download
Apache_OpenOffice_4.1.10_Win_x86_install_en-GB.exe from
https://www.openoffice.org/download/
2. Double click the file to install AOO. If you have Administrator rights it will install - just answer the questions.
Or have you installed it successfully, but you cannot run the installed AOO? If so, go Start > scroll to OpenOffice > Click Writer etc to start AOO.