This is the sticky you looked at? No Frostwire playlist in iTunes?

Double check through FW's options to make sure that iTunes sharing's enabled - just in case you forgot to click 'Apply' after making any changes to options. If that all looks fine then also check that iTunes is looking for shared libraries...

In iTunes, Edit > Preferences > Sharing > tick the box to look for shared libraries > ok.

Restart LW & iTunes... you should see 'your name's FW tunes' appear Just remember that it's only a playlist - files that you see there aren't in the iTunes library & so you won't be able to add songs from that 'FW tunes' list to an iPod or to a playlist. This sticky has lots more info (refers to LW but the LW 4 info goes for FW as well!): How to transfer music to my iPod (& iTunes) ( 1 2 3)

The exclamation mark just means that files aren't in the iTunes library.
If you're having trouble dragging & dropping from FW's library into iTunes, try a different way. Open FW, click on the Library tab & then click on Saved Files. Highlight one of the files there & click Explore (at the bottom of the page)... your saved folder will open outside of FW. Drag from that open saved folder into the iTunes library

Or in iTunes, go File > Add File To Library. Browse for FW's saved folder & add files from there.