minSDKVersion on Android?

I have installed 2.1.,2.2 and 2.3.3 API in my SDK manager and I am not sure if I am suppose to add code to the Android Manifest to indicate the minimum requirements. I received this error earlier "minSDKVersion to be set to a poistive 32 bit integer in Android Manifest"

In the Android Developers Guide is says: To declares the minimum level of the Android API that the application requires.

Am I suppose to "add" this code to the Android Manifest like this? I changed the integer to API 7 since this is the minimum installed API version 2.1 which is Level 7.

`<uses-sdk android:minSdkVersion="7" />

As you can see I'm not sure what I'm doing. Any help would be appreciated. thanx