The first step in obtaining H-1B status would be to receive an offer of from an employer willing to undergo the application process providing all the information and evidence required by the U.S. Department of Labor (DOL) and USCIS. Your employment may be full-time or part-time, but full-time is preferred. In addition, if you find yourself in a situation where two employers are willing to submit an H-1B petition for you, they can do so and you can be granted work authorization for both employers simultaneously.
Your employer must submit a Labor Condition Application (LCA) online from the U.S. Department of Labor (DOL). The LCA is your employer’s declaration that it has the appropriate wages and working conditions to U.S. workers in similar employment, that there is no strike or lockout of such workers, and that other employees have been made aware of the Labor Condition Application submitted to DOL.
Once the LCA is approved, your employer must submit and receive approval of the H-1B petition from USCIS. This petition must include a description of your employer, a description of the proposed job, and your qualifications. The H-1B petition should be submitted with the approved LCA and other evidence, such as a letter of the employment offer, a copy of your diploma, and some kind of report or brochure related to your employer).
If you leave the United States after receiving approval of and obtaining your H-1B status, your employer cannot submit an H-1B petition for you. You would have to somehow obtain the H-1B visa abroad in order to travel into the United States.