type in: 

#last

or

#cd /var/log 

#cat secure* | grep Accepted > login.txt 

The * is to read from the backup logs also omit if you don't want to see those 

this will show all successful logins 

you can also use sshd in place of Accepted to show all attempts and Accepted 

then 
#pico login.txt 
or nano or your other favorite text editor to read