Need help in alternate software serial ( Arduino Uno)

Hi, i am working on my final year project, which uses GSM Module and GPS Module on Arduino UNO. However,in order for both GSM module and GPS module to work,they must be connected to the RX pin of Arduino UNO and if i do so, they might crash together. Any ideas to solve this problem? :~

The Uno has one hardware UART, so you can connect one of your modules to that, and the other to a software serial. You can use two software serial channels, although you have to pick which you want to receive on at a given moment via SoftwareSerial.listen(). If you really need to listen actively on both simultaneously, the you can switch to a MEGA that has 4 hardware UARTs.

How can I switch to an alternate serial port? I want to use a teensy with 3 uart port, but I get a error-message about the softserial. Does somebody know whats wrong?