How to buy newly auctioned G-Sec and pledge it for margin?

I want to convert cash margin into G-Sec to earn interest and pledge them for margin needed for trading. How can I do it on Angel Broking? I am doing it on Zerodha for manual option buy trades. But I am using Angel Broking for trading spreads through API. Is it possible to buy and pledge G-Sec for this purpose on Angel Broking?