PSM is enabled by default. Configure the tracking area update (TAU) and requested active time (RAT) parameters in prj.conf:
CONFIG_LTE_PSM_REQ_RPTAU_SECONDS=7200 # Periodic TAU: 2 hours
CONFIG_LTE_PSM_REQ_RAT_SECONDS=6 # Active Time: 6 seconds
Configure a periodic TAU timer that is longer than the application's update cycle, which is the sampling interval multiplied by the storage threshold. This avoids synchronization with the network between uploads.
For additional options, see Power saving mode (PSM) in the configuration documentation. The device negotiates the actual values with the network.