Hi @hongweiyin!
Welcome!
Have you had a chance to review the "Analyzing paired end reads in QIIME 2" Community Tutorial? In particular, the section titled "Importing pre-joined reads" will get you started with importing your reads - then you can go back to the beginning of the tutorial and work your way through (skipping the "Joining reads" section, since you will have imported pre-joined reads at that point).
DADA2 works best with unjoined reads - DADA2's error model considers the forward and reverse reads separately, and joins the reads for you as part of the quality control step. If you want to work with ASVs, I would recommend working with q2-deblur (there are details on how to do that in the tutorial I linked to above).
Let us know if you get stuck or have any questions, thanks! 