We're assuming that you already have Enterprise Manager installed and up-and running.
OTR is a Java (CFML) App and for that we need to have JDK 8 or higher. Recommended is to use the JDK 8u144.
To download JDK from Oracle click here

OTR is built using OpenBD which can be downloaded here. Select the Latest Release of "Ready2Run Jetty+OpenBD".
At the moment this is the release 3.2.0

Finally we need to download the OTR Application it self.
OTR is available in 2 formats. As a .war file or as a .zip file.
In general these are identical since .war is simply just a ZIP. The zip might be easier to unzip on a Windows PC if your're to lazy to rename the file :)

The description and install instruction can be downloaded here. This file is also included in the .war and .zip files:

Downloads updated 06.06.2017