Hi, you need

1. not less then 10,000 XEM vested balance on you nano wallet
2. nano wallet can be downloaded from Nem.io official web page
3. open nano wallet and go to service---delegated harvesting  and pay the fee 0.015XEM to activate
4. then choose a node to connect, enter your wallet password and start harwesting

nodes list below you ca chooose you favofite one ))
https://nemnodes.org/nodes/

injoy harvesting !!

1-4 NEM per month is okey
0 NEM per month is ok too