fs_freemode:displayHelp(text)

This will add a notification on the top of your screen, look at the example below.

Name	Type	Description
text	string	This sets the message to display.

client.lua

TriggerEvent("fs_freemode:displayHelp", "Press ~INPUT_PICKUP~ to start shopping")

server.lua

TriggerClientEvent("fs_freemode:displayHelp", source, "Press ~INPUT_PICKUP~ to start shopping")