Staking is a method of generating consensus as new blocks are added to the Energi blockchain. The consensus is created by users who hold and stake NRG for the purpose of validating new blocks that are generated.
There is no desktop wallet for Energi 3.0. Staking is performed using a node either locally or located on a VPS (Virtual Private Server).
See below for instructions on setting up an Energi Core Node on your desktop or a VPS.