To be able to use a margin loan with StockWhip, firstly you need to enable its use. Do this by right clicking the portfolio tree item and selecting 'Add margin loan'. A Margin Loan tree item under the portfolio item will appear.
After doing that, as you purchase stocks that require more funds than you have in your cash reserve, StockWhip will ask you whether or not to automatically draw the excess funds from the margin loan.
Alternately, you can right click on the margin loan tree item and select the following options from the menu for total control over your loan balance, including accrued interest and fees. Borrowing and repaying cash obviously affects your cash reserve.
Finally, your Portfolio Page will be subtly different, showing you the Loan to Value Ratio, and other details.