Because ASEAN is not individual reporter/partner, you have to create ASEAN country group consisting all ASEAN member countries. Then in the query selection, you choose ASEAN as partner/reporter and system will aggregate data from individual countries for you.
Please refer to http://comtrade.un.org/kb/article.aspx?id=10093 for information regarding "User Defined Country Groups".
note: only registered subscriber can create country/commodity group.
As for graph, you can use other third party software such as Microsoft Excel to generate graph from downloaded data.