Despite the translation system you select in the installer, you can still configure different translation systems in a single Tridion CM, but it will be a single translation system per Blueprint hierarchy.
For instance in the picture below, 200 Content EN is an English source publication configured to use Language Cloud for any of its child publications ...
We have a demo AMI used worldwide by multiple folks to create their own AWS instances based on it, and we all share the same demo Language Cloud / BeGlobal API key without conflict. We use it to showcase the nice integration of Tridion with SDL Language Cloud.
SDL Language Cloud is enabled by default. So in installer you can just select World Server and you will get both.
If you already installed and want to add World Server to TM - see documentation
It is indeed beter to separate different translation systems in different publications. See previous answer.
Umar, welcome to Tridion Stack Exchange and Tridion in general! Hopefully you'll continue to participate in the community here and elsewhere. Your question doesn't quite fit into the Stack Exchange model. If you check out https://tridion.stackexchange.com/help/dont-ask I think you'll find that your question falls under the "every answer is equally valid" ...