You present an argument when you offer one or more reasons in an effort to support or provide evidence for a conclusion.  When you do this, you should make it quite clear to your readers that you are in fact presenting an argument, instead of merely providing information; and you should also be clear about which statement is your conclusion, and which ones are your reasons.

One excellent way of doing this is to use inference indicators: words, phrases, or even whole sentences that indicate or point toward reasons and conclusions.  A conclusion-indicator (such as "therefore") tells a reader that a conclusion comes right after it; a reason-indicators indicate that reasons come right after them (such as "because").  Here are a few typical inference indicators:
 
 

SOME CONCLUSION INDICATORS therefore so thus which proves that which shows that from which it follows that consequently which leads to which is why What follows from this is obvious.

SOME REASON INDICATORS because due to the fact that is based on is proved by is shown by which follows from is a consequence of since for There are two reasons for this. First, . . .

And here are some words that are not inference indicators:

however      but      and      moreover      in addition      or      if . . . then . . .      unless

They aren't inference indicators because they do not tell you, "here comes a conclusion," or "here comes a reason." Inference indicators do tell you (because of their basic meaning) that either a reason or a conclusion is coming next!