Here is the steps you will follow to but a ktx train ticket from Seol to Pohang on July 6th.
Step1: www.letskorail.com
Step 2: Set the options as the above image and click `inquiry'
Step 3: Select the time you want to take. NOTE: Jinsu will take the train departing at 8:35. If you choose the same train, we can travel to POSTECH together.
Step 4: Fill the infomation and pay.
Step 5: You will get an electronic ticket with a QR code. There is no gate you have to scan the QR code to open it in Seoul station. But a staff will randomly check your ticket on the train.