From targetpayandbenefits.com:
Who is eligible?
You are eligible to participate in the TGT 401(k) after you
meet the following requirements:
• You are classified by Target as an employee; and
• You are age 21 or older; and
• You complete and have been paid for 1,000 or more
hours of employment; however, if you have one full
calendar year in which you have no hours of employment
and if you previously did not complete at least 1,000
hours of employment, then you must complete 1,000
hours of employment during any subsequent period of
employment without having another full calendar year in
which you have no hours of employment.
Once you are eligible you are automatically enrolled at a 5% (the maximum match) contribution, though you will definitely want to go in and change the distribution. There is no real incentive to get Target stock, and you would generally be advised against getting it at all. The managed funds should be fine for most people. Make sure you change the company match to your preferred fund otherwise I believe it defaults entirely to company stock.