You can transfer file to an EC2/Linux host via SCP. For that you first need to have the private key file downloaded on your system. Once you have it, open the terminal window and issue the following command.
scp -i mykey.pem somefile.txt email@example.com:/home/files
For simple Linux host, you may not need to provide the .pem file, instead issue the following command.
scp somefile.txt firstname.lastname@example.org:/home/files
Hit return and provide the password for root user.
mykey.pem: Private key generated and downloaded through Amazon EC2.
somefile.txt: File that is to be transfered.
ec2-user: EC2 instance user which is created by default
ec2-123-45-67-89.compute-1.amazonaws.com: EC2 public DNS
/home/files: Location on EC2 server where somefile.txt will be saved