How many owners does your LLC have? Is it just you? Is it you and your spouse?
How you elected to be taxed as a corporation? If there are two or more owners and you are not married or you are not in a community property state, then you have to file as a partnership, if you did not previously tell the IRS that you wanted to be taxed as a corporation.
If you are the sole owner and you never told the IRS that you wanted to be taxed as a corporation, then you can file as a "disregarded entity" and use Schedule C on the 1040 return.
If you and your spouse both own the LLC and work for it and you live in a community property state, then you can each file a Schedule C, each of you claiming 50% of the business's income and expenses or whatever percentage best approximates your participation.
If you and your spouse do not live in a community property state and you both own the LLC and work in it, then you must file a partnership return (1065) in addition to your 1040.
"Note: If an LLC is owned by husband and wife in a non-community property state, the LLC should file as a partnership. LLCs owned by a husband and wife are not eligible to be "qualified joint ventures" (which can elect not be treated as partnerships) because they are state law entities. For more information see this IRS webpage.
