I'm running oracle linux 7.2.
The Oracle yum repo is comparatively small, containing only core enterprise packages.
How can I add the redhat yum repo so I can install other userspace utilities?
You should probably consider the EPEL repositories instead. Red Hat's official repository is also quite lean, and mixing Oracle and Red Hat base packages is a Very Bad Idea(TM). (EPEL is quite careful not to trample on core packages).
If you don't need Oracle support, maybe you should switch to CentOS, which is more or less RHEL rebuilt (+ EPEL, as needed), to get a somewhat wider selection of software.
For packages not available in the OEL repositories add the EPEL repository and the RepoForge, formerly RPMForge repository. You can find imagemagick in Remi's Repository. Also consider using another distribution like Ubuntu if you need access to a lot of userspace tools. You can run a Ubuntu VM inside VirtualBox which is in the OEL public yum repository.