chore(REAEME): update Swift Package Manager note (#404)

Author: jaeopt

README.md

@@ -29,14 +29,11 @@ up an Optimizely X project and start using the SDK.
 Please note below that _\<platform\>_ is used to represent the platform on which you are building your app. Currently, we support ```iOS```, ```tvOS```, and ```watchOS``` platforms.
 
 #### Swift Package Manager
- Add the following line to the dependencies value of your _Package.swift_:
+Add the dependency on the Optimizely Swift SDK with Swift Package Manager in `Xcode`
 
-```
-dependencies: [
-	.package(url: "https://github.com/optimizely/swift-sdk.git", 
-    .upToNextMinor(from: “3.7.1”))
-]
-```
+1. `File` -> `Swift Packages` -> `Add Package Dependency`
+2. Enter `https://github.com/optimizely/swift-sdk`.
+3. Accept the default rules (`Version: 'Up to Next Major'`).
 
 #### CocoaPods 
 1. Add the following lines to the _Podfile_:<pre>