Moneydance offers the ability to enter historical stock prices directly from within Investment accounts. There are a number of ways to do this, outlined below -
Manual Entry -
Open the Securities Detail view from within the Investment account, and select "History".
Click the "New" button to add a new price entry, and repeat to enter as many entries as you like.
If you have many entries you may need to scroll down to see the "New" line. 
Importing prices from your security transaction history -
Open the Securities Detail view from within the Investment account, and select History.
Click the "Import..." button. Select “Import from Transactions” and click “Import”.
The information from your security transactions will be integrated into your security’s history.
You’ll need to repeat this process for each security you’d like to import information for.
Importing prices from a file -
You can import Comma-delimited or Tab-delimited files
Open the Securities Detail view from within the Investment account, and select History.
Click the "Import..." button.
Select “Import from File” and click “Import”, then select the file containing the security price history. 
Quotes and Exchange Rates Extension -
Moneydance can automatically download price information using the Quotes and Exchange Rates extension.
Using this extension is outlined within this article from the knowledge base.