To use the RFQ feature to request data for an order, right click on the symbol on your Portfolio tab or trading tab and click Request for Quote (RFQ) followed by Submit RFQ. The Request Quote window will populate. Enter the number of contracts for which you want a quote and click OK. The market data for the selected contract will now be displayed on the selected ticker row.
Please note that this RFQ feature is available for US Corporate and Municipal bonds, and for non-U.S. options but does not cover US Treasuries.
Find more information on the Request for Quote (RFQ) orders page of the IBKR website.