Linear Time Code (LTC) is a digital audio file. You can generate your own out of a program like Reaper, but if it's more of a one-off then check out: elteesee.pehrhovey.net It will generator a WAV file for you to download.
You will need to play it via a Computer or Phone etc, and output the audio via XLR (or convert it to XLR) to be able to plug into the Fullboar. You can make/buy 3.5mm Jack to Male XLR, just crank the volume, or you can buy USB DI boxes like peavey.com/products/index.cfm/item/875/117099/ Peavey's USB-P, or many others.
So lets say that in a production there is a song that is played from a pc. I can insert in this song the timecode? without problems in the sound quality of the song?
yes you can Have a look at Reaper or any other DAW Reaper is very handy as it offers also LTC/MTC generators, markers that can be exported to cuelists etc