Every time you call or contact a lead, you should be logging it in the lead's notes. If you have called a lead, it's best to log it as a call and note just a note. Once you log a call, it will update both the Call Log and Note section of the lead.
Now click on the Call tab.
Note: Beside Calls is a # in brackets. This shows you how many calls have been logged for this lead. Right now the call log is at 0.
The call log screen will now open. Enter in what type of call it was and any notes from that particular call. Click Save Call when done.