The idea is to drop .desktop launchers into the autostart folder; these are exec'd on login. If your command has a *.desktop launcher that works appropriately (it'll be in /usr/share/applications) then the most straightforward way of having Wbar autostart at login is to copy it over to ~/.config/autostart. Failing that then another option is to create a file at
which openbox will run when it starts up. Here's an example from Trent's tutorial
about setting up Openbox to work without lxde.
fbsetbg -f -r /home/trent/wallpaper
xscreensaver -no-splash &
(sleep 2 && lxpanel) &
As you can see openbox pretty much just runs through the script and exec's the commands you put in. Note the sleep for two seconds before lxpanel gets started; you might need to do this with your Wbar if you encounter instability when running it straight away.
Hope that's helpful. Note that there are other ways of getting things to autostart on login; I sometimes feel too many. See the reply that got posted while I drafted this, their's is a system-wide solution. There are still others.