I am not us resident

As the instructions for line 5 state:

If you have a social security number (SSN), enter it here. To apply for an SSN, get Form SS-5 from a Social Security Administration (SSA) office or online at www.ssa.gov/forms/ss-5.pdf. If you are in the United States, you can call the SSA at 1-800-772-1213. Complete Form SS-5 and return it to the SSA.

If you do not have an SSN and are not eligible to get one, you can get an individual taxpayer identification number (ITIN). To apply for an ITIN, file Form W-7 with the IRS. It usually takes 4–6 weeks to get an ITIN. To claim certain treaty benefits, you must complete line 5 by submitting an SSN or ITIN, or line 6 by providing a foreign tax identification number (foreign TIN).

.An ITIN is for tax use only. It does not entitle you to social security benefits or change your employment or immigration status under U.S. law.

In your case, you should apply for an ITIN.