It should always detect your correct graphic card but sometimes the launcher refuses to display it.
You can fix it by doing this:
Backup your old config "SkyrimPrefs.ini" before using this fix.
In this config: "SkyrimPrefs.ini" there is a line
sD3DDevice="Intel (graphiccard)"
.
Cut and Paste it under the line "[Display]" and write the name of your graphiccard between the quotation marks.
example:
I'm using the NVIDIA GeForce GTX 760
-->
sD3DDevice="NVIDIA GeForce GTX 760
Also the launcher detects your 4GB correctly but 1 GB is
always automatically reservated for your OS. No PC with 4 GB RAM can run a game with 4GB. On a 8GB system you can only use 7GB effectively etc.
But the "Next" button is probably greyed out because you did not have selected the installation package like Lerrasien192 already mentioned.