You should use Asset Catalog:
I have investigated, how we can use Asset Catalog; Now it seems to be easy for me. I want to show you steps to add icons and splash in asset catalog.
Note: No need to make any entry in info.plist file :) And no any other configuration.
In below image, at right side, you will see highlighted area, where you can mention which icons you need. In case of mine, i have selected first four checkboxes; As its for my app requirements. You can select choices according to your requirements.
Now, see below image. As you will select any App icon then you will see its detail at right side selected area. It will help you to upload correct resolution icon.
If Correct resolution image will not be added then following warning will come. Just upload the image with correct resolution.
After uploading all required dimensions, you shouldn't get any warning.