If doumentation does not cover your questions or have more to ask / share with other product users or get reply from Official Support then feel free to ask / share on CodeShop Amazon Affiliate plugin Forum.
CodeShop Add New Products
CodeShop -> Add New Products menu will help you to create new post including adding products with it. As you do use simply to create new Wordpress post interface you can do same here with this page and also you will have some more extra features to add amazon products. If you want to add amazon products only with your wordpress regular posts or pages then you should use CodeShop Button documentation page how to add products with Wordpress regular posts or pages during add new posts or pages. Usually Amazon products can be added through search by text / keywords or with Amazon Standard Identification Number(ASIN). In your Add New Products post page below the post text editor you should have several boxes through which you can search / add products. Image is shown below with boxes through which you can search and add products with your post -

Select Country Box - Usually this box will show your Locale / Country what you have selected on your CodeShop Setting page in Select Country dropdown menu.
Search By Keyword Box - You will enter your search text / keyword what you would like to search on Amazon, say you would like to search 'Baby dress' or 'Shoes' , you have to put that text into this field and then click on Search button next to the search input field to get search results.
Search By ASIN(s) Box - In case of search by ASIN(s) you need to know your Amazon product ASIN numbers so you have to put them line by line means each ASIN number on each line into ASIN(s) input field, then click on Search button next to the ASIN(s) input field to get search results. you can know what is ASIN.
Products - Search Results Box - Where you should see your search results after search has been done through above one of them searching method. Usually Amazon returns maximum 10 products if found on each search results. Below image shown as sample search results while search text / keyword 'Baby dress' entered and click on Search button -

With search results 'Add Selected Products' button will be shown to add your search products, by click on this button you can add your all checked / selected products with your post. Same way Search by ASIN(s) will work to add your search products by ASINs with your post. You can add as many products as you want by searching on different texts / keywords or by ASIN(s). In case of search by many ASIN(s) at a time can take some time to get results as Amazon accepts 10 ASINs on per search request API call, say if you have 100 ASINs then Amazon will serve them through 10 API calls / requests.
You can add your different posts with different products and can put them in different product categories. You can add products categories, sub-categories through Add categories documentation page.