Site to site VPN with NAT - Step by Step guide

Hello,
 
I'll start by saying I am new to Fortigate products.  
 
I am trying to setup a new site to site VPN with NAT involved and I am new to the Fortigate firewall.  Below is the information about the Fortigate and VPN tunnel.  I looked for a step by step setup guide and have not found what I need to successfully setup a working tunnel with NAT.  I'm setting up the Fortigate side and the client is setting up the remote peer side.  Any help is appreciated.  If there is more information needed please advise.
 
Fortigate model = Fortigate VM64 (in cloud) v 6.2.3 build 1066
Fortigate WAN = 10.10.2.x
Fortigate LAN = 10.10.0.X
Local IP server = 10.10.0.28
 
Remote peer = 123.78.140.250
Remote subnets = 123.78.140.29 and 123.78.140.30
NAT IP = 10.255.12.240
 
IKE Auth Method = pre share key
IKE Encryp Algorithm = AES256
IKE Hash Algorithm = SHA 1
IKE Diff-Hellman Group = 2
Phase 1 lifetime = 86400
IPSEC Encryp Algorithm = AES256
IPSEC Integrity Algorithm = SHA 1
Perfect Forward Secrecy = Disabled
Mode = Tunnel
IP Payload Compression = Disabled
Dead Peer Detection = On
 
Thank you in advance.
John