Music in library wont go onto Ipod

Presumably, you mean that your music is listed, and playable, in iTunes, is that correct?

Once it is, connect your iPod to your computer and wait for iTunes to see it (it can take a minute or so). You'll see a small icon on the top menu bar, you click on that:

...which will present you with the Device Settings/Summary pane, which looks like the one below:

Now for a one-time setup. I suggest that you click on the Sync only ticked songs and videos (you'll see why later). Make sure that Manually manage music and videos is not ticked. Once you have done that, click on Device Settings/Music (1.) and you will see the following:

• tick the Sync music box (2.)
• choose either (3.):
  • Entire music library - which will add all your ticked songs (remember my point above? More later)
  • Selected playlists, artists, albums and genres - which will open up section 4. If you choose this, use section 4. to select the items you want to add to your iPod
• click on the Sync button in the lower right corner of the iTunes window (not shown in the screenshots)
• once the Sync completes, click on the eject iPod button, which you will see in my second screenshot, just above the battery icon. Then disconnect the cable from the computer.

That's it.

On subsequent Syncs, the iPod will update by itself, according to your sync preferences:

• • if you chose to sync the entire music library, any new music will be added to the iPod. Any revised Playlists will be updated, and so on without you doing anything
  • if you chose to sync selected playlists, artists, albums and genres, any new music in your Library will only be added to the iPod if it is in one of the previous selections you made (i.e., Playlists, or a previously synced artist or genre. Otherwise, you simply need to get back to the Settings/Music pane and revise your selections)

I'm not aware of any iPod that will not accept music on it because "it's too old".

The Recently Added section simply lists all your music in the order it was added to iTunes. That does not prevent it from going onto any iPod.

If my post above hasn't sorted out your issue, at which point in my instructions do you get stuck and why? What happens?