The screen shot your show me is not metadata. It the output from DADA2. We cannot contract a metadata based on this output. The meta should be something like following (You need to know what are those sample ID are (e.g., treatment, location.....))
Since you download the dataset from NCBI, I am guessing you cannot find the metadata fro it (The author not usually upload their metadata into NCBI).
I think if you want to learn how to use Qiime2 , please following the moving picture tutorial in the following link. It contains all the information you need to use and detail explanation. It is a good starting point.
https://docs.qiime2.org/2018.2/tutorials/moving-pictures/
Good luck!