There's a lot less that can be helped there than with production.
But, to help you out, make sure you've studied chords. When I first started music, I actually thought chords weren't that important. One very common chord progression is I vi V IV. try that out to see what it sounds like.When it comes to the lead, really just play in whatever scale you chose. Using the pentatonic version of the scale makes it much easier to write, but will leave out your ability to make some more complex pieces. Make sure to use some harder rhythms than the simple choices of quarter note after quarter note.
There are some threads here over music theory, maybe you should read those?
EDIT: whoa, we don't have a thread over chords... that was unexpected.
here's a melody thread, though:
http://www.mylittleremix.com/viewtopic.php?f=13&t=373&view=nextEDIT2: that doesn't look like the melody thread... Why does the guide link it...
EDIT3:
http://mylittleremix.com/viewtopic.php?f=13&t=1381 there you go