Here is a copy of the instructions to change the combination on your No-Key Combination padlock.
For your reference only. As the instructions note, you cannot go wrong by STRICTLY FOLLOWING THE DIRECTIONS. That said, I tried this on a spare padlock I had which was unlocked, but had an unknown combination. I used the instructions to clear the existing combination and then enter a new one of one button push.
I suggest not trying this on any padlock with a known working combination. There is no point other than to risk turning a working padlock into a paperweight.-----