It is similar as you'd "walk the cup" but as I said, you have to purge the ID of the pipe with Argon. It is tricky if you have never done it, but anything new just takes practice to get used to.
Usually, they will give you 2"-sched-40, 304L or 316L coupons. You should have a seperate flow meter to set the purge flow rate. Tape a hose to one end of the coupon(before tacking) and set the purge at 35-40 cfh and seal the other open end of the pipe. Set the gap at 1/8". There are several ways to tack it up but as I said it is tricky because you somehow have to ground the pipe while taking care to make sure the tape is tight so the argon stays inside the coupon. The easiest way to do it is to tack the pipe to the bench with the pipe vertical(4G) and then tape the hose to the bottom end of the coupon. Crank up the purge, use a gap wire and carefully put a tack (1/4" long) where there is no mismatch. Remove the gap wire and eyeball the gap opposite the first tack and place another tack. Move the coupon so the gap is even and place the final two tacks. Usually whoever is watching you do this will let you tack it up however you see fit. Examine your tacks carefully to make sure that there is no "sugaring" going on. This would indicate a leaking purge(lack of gas to the heat affected zone). To avoid this (they will bust you out for it) you have to make sure the seal is good with the tape. Assuming the tacks are "clean" you are ready to put the coupon in the 6G. Place the longest tack at the 6 o'clock position.
Now you are ready to weld the coupon and whoever is testing you will let you go for it.
I assume this part is in your capacity so You don't need any input from me, but I will say one thing: you can either set the purge at 10- 20 cfh and leave a 1/4" diameter outlet port in the tape to allow argon to escape the coupon or put that hole in the tape before you do the last quarter of the coupon. If you do if (poke a hole in the tape) before you seal up the last quarter then the inside of the root pass will be cleaner, but you risk causing concavity because the pressure(of the id purge) will push the weld out especially if the gap closes up alot. Better to put the bleeder hole in the tape before hand as examiners will accept a little color, but they will not accept a sugared root.
Be well.
Hawk