To declare a machine pool as a slave pool, where machines in the pool are slaves used to build jobs, it is necessary to configure a VMware cloud. From the main page of Jenkins click on "Manage Jenkins", click on "Configure", goto the "Cloud" section, click on the "Add a new cloud", and select "Pooled VMware Virtual Machines". Select the machine center and a pool from that machine center that shall be used as the pool of slaves. Then, configure the other parameters as appropriate. For example, if all machines are Unix machines configured with SSH with the same SSH credentials then select the "Launch slave agents on Unix via SSH".

When a build is placed on the build queue, whose label matches the configured VMware cloud, then, a machine will be acquired from the pool, powered-on (if configured), and added as node that is assigned to build the job after the power-on wait conditions have been met.

If you have selected the checkbox Only one build per VM in the cloud configuration, then after the build completes the machine will be powered-off (if configured) and released back to the pool. (In this case it only makes sense to configure one executor.) Otherwise, the slave may accept multiple concurrent builds, according to the executor count, and will remain online for a while after the initial build in case other builds waiting in the queue can use it; Jenkins will release the slave to the pool only after it has been idle for a while and does not seem to be needed.

Note that if there are no machines free in the machine pool then the build will wait in the queue until a machine becomes available.