Your client first needs to download these from Charles Schwab through Intuit Link.  You can then import the data from the 1099's via Intuit Link to ProConnect Tax.

See this article for the financial institutions supported: https://proconnect.intuit.com/support/en-us/help-article/banking/financial-institutions-supported-im...

If it is only interest and dividends, wouldn't it be quicker to manually enter those couple of numbers instead of jumping through the hoops necessary to download it?