is this a fresh install, or did you keep a /home partition from another distro or version ?
(this should already be done by default, so something's wrong)
Right-click the menu button (bottom left of screen) and select "Properties"
on the "Commands" tab set
All Settings: peppermint-settings-panel
Lock Screen: xflock4
Switch Users: lxsession switch-users
Log Out: peppermint-logout
Edit Profile: users-admin
All of those should also be ticked
DO NOT tick and use the "Edit Application" item .. there is no 100% safe menueditor for LXDE, using one will mess up your menu
The "Favourites" menu should also be populated, so as I said something went wrong .. most likely a reused /home partition ?