How can I find my w-2 for kmart online?

Contact Kmart to determine if they are making the W-2 available on-line.

If so, ask THEM how to access it.

There have been several similar questions posted over the years. The bottom line is that Whether a W2 is available on line or not is up to the company that issues them. Not all companies do. So the best and generally the only place to ask is the HR dept of the company.

Once side issue is that some of the tax programs can download W2 details if the employer made them available. The tax software can check to see if the details are available.