To generate a new key pairs

ssh-keygen -t rsa

#################

Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa): linuxwin_rsa_key
Enter passphrase (empty for no passphrase):*******
Enter same passphrase again:*******
Your identification has been saved in linuxwin_rsa_key
Your public key has been saved in linuxwin_rsa_key.pub
The key fingerprint is:
SHA256:/nnU**********************hu2c user@servername
The key's randomart image is:
+---[RSA 3072]----+
|        8===o    |
|      0++++___   |
|             =.o |
|             ...+|
|        ++++++o+o|
|       .    *****|
|        . *****  |
|        *****    |
|                 |
+----[SHA256]-----+

Install public key on the server

ssh-copy-id -i linuxwin_rsa_key.pub user@server

or just copy it to ~/.ssh/authorized_keys

cp linuxwin_rsa_key ~/.ssh/authorized_keys

Use Privete key with ssh client, mobaXterm, PuTTy…etc