Contributions to your TIAA-CREF account are part of your employer's retirement plan, like a 403(b) or 401(k). They generally cannot be counted as IRA contributions. During the initial 366-day vesting period, both your contributions and your employer's are held in an interest-bearing account. If you leave before the period ends, your money is back with interest, but you lose the employer's money. See TIAA link.
If you're interested in making IRA contributions, you'll need to open a separate IRA account. See IRS article.