Oh, I was fiddling with the x3 live the other day and I found two ways to record. One would be the way stated in the manual where u download monkey software from line6 and plug in the pod x3 live via usb.
This would be great for recording directly through a usb route as onces everything is installed, the computer would recognise your pod x3 live as a sound card. The problem i faced was that my com had no pro recording software like cubase or free ones like audicity. I only had media source programs providied by creative x-fi fatality soundcard and thus, it only supports my creative sound card for recording (ie, i am unable to select pod x3 as the sound device to draw info from in the software). It wouldn't be an issue if u had one of those recording and mixing programs.
Another way is the more analog way (but u could use the digital output as well =D ). similar to the boss gt-8 way, you could use the s/pdif output and plug it into ur sound card. if you don't have a s/pdif input on ur sound card, you could use the headphones out jack of the x3live and connect it into the line in jack on ur sond card. But I experienced major clipping/distortion issues with this method when the master volume of the x3live was too high (still happened even when my sc's amp lvl was low). There's another way to utilise the 2 XLR out jacks if ur sound card has more than one line-in but then, I think if u had that, you would know how to use it. =)
I would prefer the usb way though since its the most fuss free and the only cable u will need to handle is 1 usb cable. Not a mess of freaking expensive pro quality cables etc. I'm trying to find free DAW (programs that i was talking about) to get the x3live to work simultaneously with my soundcard as an audio device on my com. I don't have studio monitors etc to plug into my x3live's phones out so i'll have to use the com's speakers