Add link in readme to install AWS gems

Signed-off-by: AMZN-Gene <[email protected]>

MPSGameLift/README.md

@@ -2,9 +2,10 @@
 
 ## Install MPSGameLift Gem
 
-1. Open MultiplayerSample/project.json
+1. Open _MultiplayerSample/project.json_
     1. Add `"MPSGameLift"` to `external_subdirectories`
     1. Add `"MPSGameLift"` to `gem_names`
+1. [Download and register AWS gems for O3DE](https://github.com/aws/o3de-repo/blob/main/README.md) 
 1. Compile MultiplayerSample 
 
 ## Setup Instructions