connecting RF netwrok to wired network

hi all
i m new in network i need help i have two sites ( two building 4-5 km distance between them) in boths sites i have two LAN networks so connecting both sites using wired connection is not feasible due to overcowd areas. I want to connect both building using wireless RF( using high frequency) i need some help
1) what devices do i need to connect both building using RF and what devices do i need to connect RF equipment to internal LAN
2) i will highly appreciate if somebody could let me know other solution other than RF wireless technology

Regards