Hi John,
As Tony said click on the insert, you might need to hover your mouse over the text in the top left until you see the finger pointer mouse symbol then click
Just to be certain you know, the HCDB2 database is the latest official data base but is used only for writing new scenarios or editing scenarios written for that database. Database are broadly applicable to time periods so if writing a scenario for the cold war period then there is a cold war specific database available in the downloads section and if editing a scenario from eg a EC2003 series battleset scenario you would use the HCDB database (you can get the most upto date version from the downloads). the HCDB database is the standard installed database and contained in the 'commondb.res' file in your main HC folder.
If you use the latest (beta) installation downloaded from here you will be able to edit any scenario. If you use the official release installation you might not be able to edit some of the recent scenarios that can be downloaded from here as the structures are slightly different when written with the newer scenario editors. I hope that makes sense, yell if it's done nothing but confuse you
Also if you start to use database other than the installed HCDB database you need to understand how it operates. There are two basic methods:
Maintain a copy of the installed commondb.res file and ID it so you know what it is (eg put it in a folder named HCDB) and then copy the database commondb.res file you want to use into the main HC folder so as to overwrite the installed. OR
Use the HClauncher tool (https://harpgamer.com/harpforum/files/file/445-hc-launcher/) in the down loads and maintain your custom database in a logical folder structure or rename them before inserting them into HC folder.
again, if I've just confused you give us a yell, but most importantly enjoy harpoon