How to add seed nodes in altcoin? I have made an altcoin in my local machine running MacOSX. I have purchased amazon ec2 and compiling the daemon to running in unix.

How do i add seed nodes?

I see that there are two files chainparams.cpp and chainparamseeds.h. 
What is the difference between these two files?

chainparams.cpp

vSeeds.emplace_back("dnsseed.thrasher.io", true);
vSeeds.emplace_back("dnsseed.litecointools.com", true);
vSeeds.emplace_back("dnsseed.litecoinpool.org", true);
vSeeds.emplace_back("dnsseed.koin-project.com", false);


chainparamseeds.h

static SeedSpec6 pnSeed6_main[] = {
 {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0x05,0x53,0x80,0xc7}, 9333},
    {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0x05,0xa4,0xdf,0x66}, 9333},
    {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0x05,0xff,0x56,0x07}, 9333},
    {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0x0e,0x98,0x79,0x2d}, 9333},
    {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0x0e,0xa2,0xd0,0x9d}, 9333}
The domains listed in chainparams.cpp are for DNS seeders. DNS seeders are not nodes themselves, but rather are DNS servers that serve the IP addresses of nodes that are available to be connected to. These can be connected to for both a normal connection and just one to retrieve more IP addresses of nodes.

The IP addresses listed in chainparamseeds.h are the IP addresses of nodes that can be connected to. This connection can be an actual connection or just one which retrieves more IP addresses of nodes that can be connected to.

To setup a seed node, you just need to run a normal node for your altcoin and add its IP address to chainparamseeds.h. There should be a script that actually constructs this for you in contrib/seeds.

To setup a DNS seeder, you will need special software to do that for you. You can start with this software and modify it as necessary to work with your altcoin.