You have to create the link so:

create database link el_sur
connect to usuario identified by clave
using 'El450Sur';

usuario is the user;
clave is the password
el_sur is the link's name.

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Then in $ORACLE_HOME/network/admin/tnsnames.ora
add it

El450 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL= TCP)(Host= enel02)(Port= 1521))
(CONNECT_DATA = (SID = conv))
)

enel02 is the name of the remote machine, conv is de database name.

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Now you can do it:

select * from your_table@el_sur;