One of the menu options under the Contact Overview menu that is accessible when within a contact record is the Know Your Client section of the contact record:
After clicking Know Your Client, you'll then see the Know Your Client area for the contact and can begin filling in your applicable information for them.
Here, let's look at the Estimated Net Worth section of this page:
If no data has been entered here, it will be blank as above. To add data, just click the Edit button in the top right corner of this section. You'll then see the below:
Enter the client's estimated Assets, Non-liquid Assets and Liabilities here and this section will look similar to the below, based upon your numbers:
Estimated Net Worth and Estimated Liquid Net Worth are calculated automatically, based upon the numbers you enter for Estimated Assets, Non-liquid Assets and Liabilities.