your paintings, sculptures, dance/music performances, jewellery creations, drawings, knitting works, creative writings/poems, photography, etc etc

go work! work! work!

given your previous post I take it you mean your portfolio to get into undergrad, not a portfolio of undergrad work.

here are some possibilities:
1) they may not require you to submit a portfolio at the start. Many schools place you in a pre-arch program for the first two years and then the actual arch program for the final two years, you may be required to submit a portfolio from the first into the latter but none into the first.
2) general creative work, drawing, painting, photography, etc.
3) they may have a preliminary design task for you to complete and submit to them

So... it depends on the school.

Hello--ACSA here! 

Just want to give a plug for the architecture college fair coming up in San Francisco on Sept 28, as well as in Boston on October 26. Portfolio reviews will be a part of both events so you can bring a draft of your portfolio (or just your questions) and get some advice in person.