To view the products in Bestsellers Insight section, you should log into your AliDropship account. If you don't have an account yet, you should register.
Enter your email and click Register. You'll get the letter with a register link and your login information. Click the button in the letter. You'll be redirected to your AliDropship account.
To add a product from Bestsellers Insight to your store, copy its title.
Paste this title in the search field in Import products section of AliDropship plugin.
Then click the Import button. The product will be added to your site.