It's important to follow the Installation Instructions. If you attempt to install ORA without following those instructions, you are likely to fail.
You can download the install program for the latest version of the ORA host component, version 1.73, using the following link:
Your antivirus software may not trust the ORA installer because ORA is a new program and has not yet earned enough reputation points to convince antivirus software makers that it can be trusted. You may have to instruct your antivirus software to allow you to download the installer if that software deems it suspicious.