How do I file taxes if I'm self employed?

You should consult a tax professional for a detailed analysis of your situation.  It will depend on how your LLC is treated for tax purposes, both at the federal level and at the state level.  If the LLC is treated as a sole proprietorship or "disregarded entity" then the income is shown on schedule C of your personal tax return and a corporate return is not needed.  If the entity is treated as a partnership, S-corp or C-corp for federal and/or state tax purposes then it may be necessary to file a corporate tax return.  It is important that you consult a tax professional to assess your particular situation.

It depends on how your LLC is taxed. An LLC can be taxed as an S-Corporation, C-Corporation, partnership, or sole proprietorship.
Craig W Smalley EAAdmitted to Practice before the Internal Revenue Service

You would want to file a regular 1040 and itemize your business income and expenses on Schedule C.  In most cases, people who fill out Schedule C will also have to fill out Schedule SE, "Self-Employment Tax."
But you should probably talk with a tax professional to ensure you are filing all the proper forms.