You must apply (or reapply) for a U.S. Tourist (B1/B2) visa on the U.S. embassy website. You do not need an agent if you can read and write. Applying does not equate to approval. All who apply are presumed ineligible. There is no guaranteed visa approval (regardless of who fills out your online visa application), and the grounds for any prior denials must be overcome. Your eligibility for a visa depends on your personal situation where you legally reside, not on anything anyone in or outside the U.S. says or does. I have several posts on my page on tourist/visitor visas that you should read.
What are These Visas for?
Tourist visas are strictly for short visits for pleasure – you must overcome the presumption of ineligibility. If you are applying for the visa to work, seek work, study, relocate, or give birth, you are not eligible for a tourist visa, and will be denied. The interviewing officer decides based on your personal situation in your country, as revealed in your visa application and your past trips to the U.S., if any, whether you are likely to violate the visa conditions (such as you may be seeking employment in the U.S., coming to give birth, or you are likely to remain in the U.S.).