how to import dvd rental database on mac. The postgres tutorial only gives instructions for windows

I have downloaded the dvd rental.tar file on my desktop. followed the below instructions

pwd
/Users/O2/tools/postgres
mkdir dvdrentaldb
initdb dvdrentaldb

I get the following message

initdb directory "dvdrentaldb' exists but is not empty If you want to create a new database system either remove or empty the directory or run initdb with an argument other than "dvdrentaldb"

I have downloaded the dvd rental.tar file on my desktop. followed the below instructions

pwd
/Users/O2/tools/postgres
mkdir dvdrentaldb
initdb dvdrentaldb

post this i am using the following code

pg_restore -U O2 -d dvdrentaldb dvdrental.tar

i get syntax error at or near "pg_restore"

I get the following message

initdb directory "dvdrentaldb' exists but is not empty If you want to create a new database system either remove or empty the directory or run initdb with an argument other than "dvdrentaldb"