How to add log out button on desktop panel (manual for newbies).
Right mouse button click on free revenge of the panel.
Go to "
Panel->Add New Items".

Click on "
Launcher", then click "
Add" button down.

It creates button in panel.

Right mouse click on newly created button. Go to "
Properties". Add a new empty item.

Write in fields:
"Name" - "Logout".
"Command" - "peppermint-logout".
In field "
Icon", choose your favorite icon for your button. I chosen "system-shutdown" icon. Then click button "
Create".
Thats all! Have fun!
P.S. The same way, you can add other buttons.
Field "Command" <- "shutdown -r now" # for immediate reboot.
Field "Command" <- "poweroff" # for immediate shutdown.
Field "Command" <- "lxsession switch-users" # to switch users.
Field "Command" <- "xflock4" # to lock screen.
Field "Command" <- "peppermint-settings-panel" # for peppermint settings panel.
and etc...