Correct spelling, explanation: the word stepping is a present participle/gerund of the infinitive to step. It originates from Middle English steppen and from Old English steppan. If we want to create a derivative of this verb, we must add the regular -ing suffix to its basic form of it. In this case, we should also double the -p letter due to an important rule: when there is a single vowel before the last, stressed consonant in a word, we need to double that consonant. Therefore, the only correct form is stepping, not steping.

Definition of stepping:
verb (present participle), to press down with the foot
You’re stepping on my foot!
He hesitated before stepping down the stairs.

Collocations with stepping:
Some most commonly used collocations include: to step gingerly and to step bravely.
He stepped gingerly into the river and waded out to the center.
It was Ethan who bravely stepped up to the door and rang the bell.

Incorrect spelling, explanation: steping is a misspelling, but a quite common one. Many English users tend to forget that the last (and stressed as well) consonant in a derivative must be doubled if there’s a single vowel before it. Always remember that principle when creating a present participle/gerund form of a verb. Therefore, the only correct version is stepping and steping is incorrect.