I did this recently with my OL Silver mkii tonearm. See the 6moons article below for a diagram (scroll down to the bottom). In my case I just used some radio shack jumper cables and connected them between my receivers L/R preouts ICs and the tonearm wire clips. I then connected the tonearm RCAs into a line level input on my preamp. Finally, I just played cable radio station music via my reciever through the tonearm cable until I felt it was toasted enough. It worked like a charm!
http://www.6moons.com/audioreviews/originlive/silver_2.html
Listening Impressions Round 2 Using a CD Player Output to Burn In the Tonearm Cable
Origin Live says Origin Live arms take a very long time to burn in their cables and do not sound anything like the final performance when first used. To speed up this process we offer the burn in cable which speeds up the process enormously. Origin Live recommends that you burn in the tonearm cable using the output of your CD player and the supplied burn-in cable for a minimum of 24 hours. Essentially you turn the tonearm cable into a high-level interconnect with voltage passing through it from the CD players output that is thousands of times greater than it will ever see from any phono cartridge.
http://www.6moons.com/audioreviews/originlive/silver_2.html
Listening Impressions Round 2 Using a CD Player Output to Burn In the Tonearm Cable
Origin Live says Origin Live arms take a very long time to burn in their cables and do not sound anything like the final performance when first used. To speed up this process we offer the burn in cable which speeds up the process enormously. Origin Live recommends that you burn in the tonearm cable using the output of your CD player and the supplied burn-in cable for a minimum of 24 hours. Essentially you turn the tonearm cable into a high-level interconnect with voltage passing through it from the CD players output that is thousands of times greater than it will ever see from any phono cartridge.