Instrumenting the PostgreSQL server means adding a namespace with some administrative tables and (on older servers) some support functions to the maintenance database (usually the "postgres" database). To instrument the server, use the context menu. The server's instrumentation status is displayed on its property page.
To fully instrument older PostgreSQL servers, some preparation is necessary that is outside of Admin4's scope. Most notably, for PostgreSQL 8.1.0 to 9.3.x, the adminpack extension package needs to be installed on the server. If installed, Admin4 can continue and register the extension.
In order to enable the Admin4's configuration tool, the main postgresql.conf file needs to be extended. On some installations (e.g. debian), the postgresql.conf file is not located in the data directory, but somewhere else, and thus cannot be changed using adminpack's write routines. In this case, a hint message with installation instructions is displayed; perform this step manually as advised. Admin4 creates and maintaines a postgresql.auto.conf file in the database directory (this mimicks the behaviour of PostgreSQL 9.4 and up), which has to be included in the main postgresql.conf file using a directive like
include '/path-to-datadirectory/postgresql.auto.conf'
In general, it's no problem to run Admin4 on a partially instrumented server, you only will miss some functions.