Need help on how to change the SSH username and password on my Cisco 9300 switch and also 5516 ASA firewall

(config)# username cisco secret password_etc

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(config)# hostname switch
(config)# ip domain-name your_domain.com

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(config)# crypto key generate rsa

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(config)# line vty 0 4 
(config-line)# transport input ssh 
(config-line)# login local

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You don't need to change the hostname/domain and regenerate the SSH key to change the SSH user/pass. Telnet and SSH will use the same credentials.

Post the config for your devices (omitting any sensitive info like IP addresses, identifying names, etc.) and we can tell you exactly what to do. There's a couple of ways depending on whether you're using aaa new-model or not.

Thanks for your help.  so currently on my 9300 switch, it has a password set for "ABCDEF" (not the real password - just representing the password).  If I want to change it to "ABCDEF123" - and if the Telnet password and SSH password are the same - why doesn't it change when I change the Telnet password?  

This is how I changed the Telnet:

#config t
#line vty 0 4
#password ABCDEF123
#exit

shouldn't that change the SSH password then?

The telnet and SSH passwords are one and the same. The transport protocol is irrelevant.

If you can telnet but not ssh it's probably because there's no username configured, or the switch isn't configured to use one, hence asking for the running config. 

gotcha. here's the run config...9300.txt

very sorry i forgot to come back on this one guys.  I appreciate your help, and your suggestions worked.  i'll give the points out...