You should leave it blank unless you have an EIN other than your social security number. However you can also go online and get one in a very short time! https://tax-irs-ein.com/?hour&utm_term=apply%20for%20ein%20number&gclid=Cj0KCQiAt_PuBRDcARIsAMNlBdpQ... "apply for ein number online IRS" You can have a number and print out a letter with it in less than an hour.
The E refers to Employer, so you definitely need this number if you employ anybody. If you don't, and you are filing a schedule C, it is possible not to have a number. If TT won't allow you to proceed, you could try putting in your SS#, but be sure you delete it before filing as the EIN is not the TID (SS# also known as Taxpayer ID).