How do I claim the California credit for taxes paid to another state?

Taken from California Instructions for Schedule S, Section C & H

California resident individuals that earned income from sources within any of the following states and paid net income tax to that state on income that is also taxed by California may claim the other state tax credit:

California residents who filed a nonresident return with Arizona, Guam, Oregon or Virginia may claim the credit on the nonresident return instead. Check the nonresident state instructions to determine if you should file the credit on the nonresident return rather than the CA resident return. 

California Non Residents 

California allows Oregon residents to claim a credit for taxes paid to Oregon on the California Non Resident return. 

Where to enter the credit

To add the credit for taxes paid to another state, please follow the steps below:

1. Click State on the left side menu
2. Click the three dots to the right of your state and select edit
3. Select "Begin" under Credits
4. Select "Begin" under Schedule S, Other State Tax Credit
5. Click the +Add Credit box
6. Enter your information into the form and click continue. 

*Please note that you will need to do this for each state you need a credit for