ssh-keygen

Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa):

Enter passphrase (empty for no passphrase):
Enter same passphrase again:

Your identification has been saved in /home/username/.ssh/id_rsa_ubuntu.
Your public key has been saved in /home/username/.ssh/id_rsa_ubuntu.pub.

The key fingerprint is:
SHA256:nNnQckFbuegUs4WD3y+7YqwCaDhfUlX2J17jxF7X3FU xenby@demo.com

The key's randomart image is:
+---[RSA 2048]----+
|       .o++ ..  E|
|      .  *o+.  ..|
|     .  = *+ o ..|
|    .  . Ooo+ * +|
| . o    Soo..B o.|
|o + o     . ..o  |
| + o .   .  . .  |
|  .   .   +  o   |
|       ..o .o.   |
+----[SHA256]-----+

ssh-copy-id -i your_key_path username@server_host

/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys         

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'username@server_host'"
and check to make sure that only the key(s) you wanted were added.

scp -i your_private_key_path username@server_host:file_path local_path