I am not sure what you expect, but most people here don´t read other´s minds and don´t have other superhuman abilites. I have no idea what that GSMSim900D is or how it is connected. So unless you post a datsheet and a diagram of how you want to connect it you will get very little good responses. And bumping the thread won´t get you much help either.
So, are you trying to communicate with the GSM module through UART, or SPI? You mentioned UART connections, from the Arduino to the computer, so you'll either have to do a software UART, or use the SPI interface...
Draw a schematic to help the people trying to help you.
since there is only one tx-rx pin in arduino and also in the GSM module,. how can i interface the RS232 to ttl converter?
or anyone of you try doing that without bricking one of the device? tnx
And those DTR, DCD, RTS and CTS pins are there just for fun? If the modem needs them to communicate then you will have to connect those as well. But I have a feeling that you need to put your own program inside the modem, so I guess that is up to you.
Also, why do you need RS232-to ttl converter when both arduino and the modem use TTL levels? (one could be 5V and the other 3.3V though)