PSM is enabled by default. Configure TAU and 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
It is recommended to configure a periodic TAU timer longer than the update cycle (sampling interval * storage threshold) of the application to avoid synchronization with the
network between uploads.
See the Configuration guide - PSM for additional options. The actual values are negotiated with the network.