If you and your partner are in a registered domestic partnership (RDP) and you reside in the community property states of California, Nevada, or Washington state, you'll each need to prepare your own federal tax returns based on your state's community property rules.
You'll both report your share of community property income, which is determined by your state's tax laws and other factors like prenuptial agreements.
We can't figure out what your share of community property is. Each couple will need to determine this for themselves. IRS Publication 555 (page 3 in particular) has guidance on how to determine and properly split community income.
If you choose to jointly file your California state return, we recommend switching to the TurboTax CD/Download software instead of TurboTax Online. It simplifies things and will also save you some money. Additionally, our instructions in Part IV are geared toward the software.