How to add an userA to login postgresadmin

Hi folks,

RH8.0
postgresql-7.4.3.tar.gz

I have postgresql-7.4.3 installed

$ whereis pgsql
pgsql: /usr/local/pgsql

and have created "postgresadmin" for root
# adduser postgresadmin

root can su postgresadmin without password

Now I expect to add 'userA' to login as postgresadmin
with a password

Can I perform following step to reach my goal;

# adduser userA postgresadmin passwd xxx

Kindly advise. TIA

B.R
Stephen

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