Hello. We recommend that you keep the software version that come in the standard repository system. For new versions of software can in principle use the dotdeb repository (
http://www.dotdeb.org/). Nginx also can be installed from this repo.
To install Nginx into server use the
Applications menu in ISPmanager
After software upgrade run '/usr/local/ispmgr/sbin/pkgctl cache' command in shell for update cache information for Application menu