If you go to Google and have a search for Yiwu market address/locations, you will find a bunch of sites following telling / showing you where Yiwu markets are. Be aware, most of these addresses are not useful to you at all.
In fact, among a dozen of different markets in Yiwu, there are only two that you will probably visit: Yiwu International Trade Center and Yiwu Huangyuan garments market. You can now forget the rest of them totally.
Yiwu Market Address - Yiwu International Trade City
In fact, you don't need the address of Yiwu market. Everybody in Yiwu knows this place. This is just like everyone in New York knows where The Times Square is and everyone in London know where the big clock is. (Not sure if this a good example as i personally never been there)
What you need to know is the Chinese name, which is 国际商贸城. You just show everyone and they will tell you the direction. Don't worry to copy these few Chinese characters now, you will find a downloadable PDF file at the bottom of this page.
Huangyuan market actually has a longer history than Yiwu main market-Yiwu International Trade City. Although this market was rebuilt into a garments market, still most of Yiwu people know where it is - at the corner of Jiangbin Bei RD. and Huangyuan Rd.
In Chinese: 江滨北路和篁园路交叉口.
The Chinese for Huangyuan market is 篁园市场. As usual, you can find this in attached PDF file.