setting up .ssh directory so that I don't have to enter password everytime I do scp command

I've see this post but couldn't exactly follow it. (https://superuser.com/questions/8077/how-do-i-set-up-ssh-so-i-dont-have-to-type-my-password )
I want to access from machine A(local) to machine B (remote).

What I did was :

1. I copied the .ssh/rsd_isa.pub of machine A to machine B's .ssh/authorized_keys file.
2. I checked the write permission is off in machine B's .ssh/authorized_keys file.I tried accessing machine B from machine A like this :
   scp ckim@123.456.789.10:/home/ckim/file1 .
   But it asks me the password.

The link above told me to "load the key to the ssh agent". But I couldn't understand that part. I tried this one :

ckim@ckim-ubuntu-22 ~/.ssh $ ssh-agentSSH_AUTH_SOCK=/tmp/ssh-XXXXXXipqtBR/agent.1234456; export SSH_AUTH_SOCK;SSH_AGENT_PID=123456; export SSH_AGENT_PID;echo Agent pid 123456;

So am I supposed to execute this commands where? in machine A? (actually I tried it and also tried ssh-add command, but machine B asks me the password when I access it from machine A).How should I do it?