Just access the first router in the normal way then use the telnet or ssh command to access the second router.
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You need to configure the vty lines on one of the routers, so that you can either telnet or ssh to it.
On one of the routers, enter the following from global configuration mode, (router would be your router hostname):-
router#(config) line vty 0 15
router#(config-line) password cisco
Save this and it should allow you telnet from one router to another.