I try to claim my stepdaughter as a dependent but I don't know how to do this right since there is no stepdaughter section only daughter and son

Your Two possibilities to claim a dependent are as follows:

You may be able to claim your stepdaughter as a Qualifying Child dependent if:

1. The child must be related to you. The child can be your son, daughter, stepchild, eligible foster child, brother, sister, half-brother, half-sister, stepbrother, stepsister, adopted child or an offspring of any of them.
2. Your child must be under age 19 or, if a full-time student, under age 24. There is no age limit if your child is permanently and totally disabled.
3. Your child must live with you for more than half the year, but several exceptions apply (i.e., away at school).
4. The child cannot provide more than half of his/her support.
5. You must be the only person claiming the child
6. The child must be a US citizen, resident alien, national, or resident of Mexico or Canada.
7. The child cannot file a joint return with his or her spouse.

You may be able to claim your stepdaughter as a Qualifying Relative dependent if:

1. You provided more than half of her support in 2016
2. She earned less than $4,050 in gross taxable income. (Social Security income generally doesn’t count here.)
3. She lives with you 365 days in the year or is related to you.
4. She isn’t a dependent on someone else’s tax return.
5. She isn’t filing a tax return with a spouse (married filing jointly).
6. She is a U.S. citizen, resident alien, national, or a Canadian or Mexican resident

Here's how to add a dependent in TurboTax.

• Open your return (if you are not already there).
• Click on Orange box 'Take me to my return' (if shown).
  
• Click the Personal Info tab.
• On the Personal Info Summary screen,
  
• Scroll down & Click on "+Add a dependent."
• Under "Who do you support," Choose the first option "My child (includes adopted, foster and stepchildren)."
• Click Continue to input your stepdaughter's info.
  

I am confused by this. I did the how to add a dependent but then in the tell us about your child I don't know what to pick. if i pick daughter (which she is not, she is my stepdaughter) it works but if I don't pick that no credit's are applied
also, what does child needs to be related to me mean ? she is my stepdaughter but that doesn't make her related to me. I pay all her healthcare since she is on my family plan, food, the lives in our house, i pay phone, internet, uber, etc.

For tax reporting purposes she is considered your daughter.