Carlesa, if you don't have current statements, check with the human resources (HR) department for your employer. They will point you in the right direction. It is a good idea to review your 401k holdings at least annually, although most people review them quarterly.
A few things to keep in mind:
1) Early withdrawals taken before age 59 1/2 are typically taxable as income AND carry a 10% penalty.
2) You should at minimum be contributing 5% of your income to your 401k. Contributions may lower your income taxes and will help you accumulate funds for retirement. Some employers also offer matching contributions (free money!)
3) If choosing among investment options is overwhelming, consider a "target fund" that specifies the desired year of your retirement, or consult a certified financial planner.
I hope this helps!