What should be the total amount for that line?
Use the IRS website for a federal tax withholding calculator - https://www.irs.gov/individuals/tax-withholding-estimator
You will not be able to file a tax return as "Head of Household" if you do not have a qualifying dependent.
Am I Head of Household?
https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household
https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household
If you qualify as Head of Household, when you enter your marital status (single or married filing separately) into MyInfo, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.