It's easy to upload to the site; go to the advanced message editing mode (button at the bottom), and you'll see the "manage attachments" button below the editing window. Click it, upload the attachment (in the case of a map, you need to archive it in zip first). Done. In the case of the hut, pay attention to "Parameters" (the line is just below Kind). Right-click on it, select Add, and enter the script name of your assassins there. Regarding the lava and swamp, use the Erase tool in the same tab where you placed the swamp and lava. Regarding the hero, the advice is the same as for the assassins, only the script name needs to be looked up differently. You need to select the hero, press the spacebar, go to Settings, and look at the contents of the Name field.

I read the topic about creating a video, the editor is expanded, I go to View, then Database, then GameDatabase Window, I click on the database window, and then nothing happens, the window just closes.

There, you should probably click New Database Window. Maybe you also need to mark it with a checkmark afterward; I don't remember.