First, you need to see what platform you are going to sell on, and secondly, what category of products. Then, you need to look for a suitable source of goods on Alibaba. After finding the source of goods, contact customer service to ask for a picture package or data package, and then you can start uploading pictures and publishing products. If there is an order, you can directly place an order through Alibaba consignment sales or wholesale orders. This depends on the specific operation mode of the upstream supplier you are looking for.