Guide For People Who Don't Want To Mess With Oscillators
The 'TripleOscillator' is kinda presented as the default way to make sounds in LMMS, but that kind of synthesis is complex! Here's a guide for making stuff in LMMS without using it. Personally (— rjt (talk)) I think it's good to get a bunch of different sounds going with as little fuss as possible.
In the 'Instrument Plugins' panel on the left you should have one called 'ZynAddSubFX'. This gives you access to a bunch of poorly organised, but diverse instruments. If you drag that onto the 'Song-Editor' you'll be able start messing with it.
Once it's there double-click on the text and it'll open a settings window. A similar window opens for other instruments too. Ignore most of the stuff there for now and click on 'Show GUI'.
If it prompts you asking if you want to use 'Beginner' or 'Advanced' mode just pick beginner. You should see a window with piano keys at the bottom, a box on the right with the text 'No Effect', and a box to the left of that, which is what we want. Click on the blank bit in there and you'll get a new window where you can select different instruments. You select categories from the pull-down menu, and single-click instruments to select them. If you have a tune playing, or if you press keys on the virtual keyboard (or MIDI one if you have one setup) you can hear it too.
NB: There's a quicker way to get to the different ZynAddSubFX instruments, I just don't usually use it because the preview isn't as nice. Select the 'My Presets' and you'll see a directory browser like in a file manager. Open the 'ZynAddSubFX' one and you'll have all the same instruments in there. You can preview a single-note but single-clicking, and can make a track with that instrument by double-clicking or drag-and-dropping.
If you look at the very left of the screen there are some tabs. The 'Instrument Plugins' one's usually open by default, but there are other you can select that give you access to other stuff on your computer. The third one down should be 'My Samples', which has a bunch of useful snippets in OGG format. Click on things once to hear them, and double-click to make a new track with that sample in your 'Song-Editor' or 'Beat+Bassline Editor'.
From here you can program it with the piano roll or whatever's your preference, as usual.