add spm below the installation guide section

README.md

@@ -158,11 +158,21 @@ How to debug CloudKit in production mode? See this [post](https://stackoverflow.
 
 ## Example
 
-To run the example project, clone the repo, and run `pod install` from the Example directory first.
+To run the example project, clone the repo, then open the `Example/IceCream_Example.xcodeproj`.
 
-## Installation
+## Installation Guide
 
-Using Carthage or CocoaPods.
+Using Swift Package Manager, Carthage or CocoaPods.
+
+### Swift Package Manager
+
+From Xcode 11, you can use [Swift Package Manager](https://swift.org/package-manager/) to add IceCream and its dependencies to your project.
+
+Select File > Swift Packages > Add Package Dependency. Enter https://github.com/caiyue1993/IceCream.git in the "Choose Package Repository" dialog.
+In the next page, specify the version resolving rule as "Up to Next Major" with "1.13.1" as its earliest version.
+After Xcode checking out the source and resolving the version, you can choose the "IceCream" library and add it to your app target.
+
+If you encounter any problem or have a question on adding the package to an Xcode project, I suggest reading the [Adding Package Dependencies to Your App](https://developer.apple.com/documentation/xcode/adding_package_dependencies_to_your_app) guide article from Apple.
 
 ### Carthage