With Squish plug-in for Jenkins there are multiple ways to configure Jenkins to point where Squish is installed.
The first step you need to do is adding Squish installations in the Global Tool Configuration .
Once the installations are defined you can easily select one of them as a Squish Package in the Squish step configuration.
For each Squish installation you can provide a hardcoded path. This path will be used whenever the installation is selected in the Squish step configuration.
In order to have full flexibility we don't have to pre-set the fixed Squish installation path in Jenkins Global Tool Configuration and use an environment variable for that purpose. With this solution we can set Squish location per Job, per Agent or even dynamically set during Job execution taking advantage of environment variables handling in Jenkins. Of course any environment variable name can be used.