connect to database. run it like a sql.

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发件人：Ze Victor Harry<assayabadi@gmail.com>
日　期：2018年08月03日 16:14:25
收件人：<pgsql-bugs@postgresql.org>
主　题：how to enable pgcrypto

hello again I have a small problem here can someone tell me briefly how to do it? I am getting this error 

When i give ant fresh_install it gives error PostgreSQL 'pgcrypto' extension installed /up to date? False (not installed) Create extension pgcrypto.

I have tried to look up for solutions and they all say I have to run a command 

# Login to your "dspace" database as a superuser

psql --username=postgres dspace

# Enable the pgcrypto extension on this database

CREATE EXTENSION pgcrypto;

 but where I got confused is from where do i run these commands.is it from cmd? or in pgadmin sql? I need clearly articulated  steps