If you are owner or part owner in a S corp, you need to file the Corporation's taxes on the Form 1120s. My best advice to you is, do not attempt to file this form yourself. You need a tax professional such as an Enrolled Agent or CPA. The rules for filing an 1120s are complex and require knowledge as to what expenses can and cannot be taken by an S corp.
When you incorporate your company, you must file for the S corp election by filing the IRS Form 2553. If you do not file this election timely, you will have to file the form 1120 and the company will pay taxes at the corporate tax rate. If you file the S corp election and it is approved by the IRS, you will be taxed at your individual tax rate.
Your 1120s is due on March 15th if you are a calendar year company and 2 1/2 months after the end of your fiscal year, if you are a fiscal year corporation. You may file for an extension just as you can for your personal income tax.
Once the 1120s is completed, each owner will receive a K-1 that they will file with their own 1040 return. Your percentage of the company's profit or loss depends on your percentage of ownership of the corporation.
You may have received a salary during the year, so you may have both a W2 which reflects your salary paid throughout the year and the K-1 which shows your portion of the corporate income or loss.(regardless of whether or not you actually received this money, it is still your portion of the income earned or the loss incurred)
S corps can take most reasonable business expenses, including the owners' reasonable salary. You will need your previous years tax return(if you have filed before) and your companies profit and loss statements as well as your balance sheet, for your tax preparer to be able to prepare your return. They will also need to know the date your company was incorporated.
Hopefully you consulted with a tax professional when you set your corporation up. You have to make decisions about your accounting method and many other business decisions. Being sure you make good decisions up front and knowing about record keeping requirements will make tax time go much more smoothly for both you and your tax preparer.
Do your homework and find a competent tax professional who can help you make good business decisions and help you file your tax returns correctly and on time.