There's a tab on the bottom of the spring that engages a slot in the frame.
Also, I have found that if the grip safety is in place while trying to install the sear spring, it can be almost impossible to get it in right because you can't see exactly where the tips are. I always put the grip safety in after the sear spring is in place. I slide the main spring housing partially in to retain the sear spring.
There's a step by step tear down/assembly guide on the 1911 home page. You should read it, and compare the instructions to one of those exploded views.
Also, I have found that if the grip safety is in place while trying to install the sear spring, it can be almost impossible to get it in right because you can't see exactly where the tips are. I always put the grip safety in after the sear spring is in place. I slide the main spring housing partially in to retain the sear spring.
There's a step by step tear down/assembly guide on the 1911 home page. You should read it, and compare the instructions to one of those exploded views.
