The Name parameter of the deeplink is always the identifier that directly follows 'link/' in the URL; in your case "deeplinkName". Any GET parameters following that (like '?argument=Argument') are automatically translated to microflow parameters without any configuration being necessary. If the microflow you are calling with your deeplink has a String argument called 'argument', that parameter will receive the String "Argument".
*Edit: Note that the URL shown in the configuration screen is just an indicator of what a possible URL might look like, and might not be complete in all cases. If you configure a deeplink called 'Example', both the URLs "myapp.com/link/Example" and myapp.com/link/Example?param=foo¶m2=bar" are valid ways to call the link. (Though the first will not pass any parameters to the microflow)
*Edit2: I understand you're actually talking about building a link for a user to click on. The deeplink configuration (which has the Deeplink/Name parameter) is just something that tells the runtime "when a user comes in with a URL that contains "/link/<deeplinkname>", call this microflow". Actually creating such a URL, for instance in a e-mail, is something you should do yourself.
When you create the e-mail text, you can create a link to e.g. "'http://myapp.com/link/FillForm?user=' + $UserName". You do not need to use the CreateDeeplink microflow for this, since the deeplink (configuration) already exists. Just create a String containing that URL and put it somewhere in your e-mail message. You can use a microflow to build the e-mail text as a String, or you can use the e-mail template module to do this more easily.
The link should be http://myapp.com/link/deeplinkname/argument.