To reserve a machine for a build go to the configuration page of an appropriate job, go to the "Build Environment" section, select "Reserve a VMWare machine for this build", and select the machine center and a pool from that machine center that shall be used as the pool of reservable machines.

When a build of such a configured job is placed on the build queue then, the build will start, a machine will be acquired from the pool, powered-on (if configured), and the build will wait until the power-on wait conditions have been met. After the build completes the machine will be powered-off (if configured) and released back to the pool.

The build itself is not run on this machine; it is merely made available. To actually use the VM from your build, you would need to somehow connect to it, typically using the VMIP environment variable.

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

You may also select multiple machines. In this case all of the build will proceed once all of them are available. (The build may tentatively acquire some, release them, and later reacquire them, to avoid deadlocks.)