In the application navigator filter text box, type Virtual War Room, and you'll see the virtual war room application header, as well as the Virtual War Rooms module (automatically pluralized based on our table label). Click on that module, and you should see the Virtual War Rooms list view.
The columns displayed in the list view of a given table, such as the request item (sc_req_item) table, can be either personalized (modified just for you) or configured (modified for all users). You can choose to display any field within a given table in the list view, or even derived fields (fields with data from related records).
If you don't see the Major incident column in the Virtual War Room list view, click on the hamburger menu at the top-left of the content frame, and click on List Layout. On the next page, find the Major incident field in the list marked Available, and either double-click it, or select it and then click the right-arrow to move it over to the Selected box. Next, make sure you have that field selected and click the up-arrow on the right, until it's listed right after Short description.
While we're here, let's remove some superfluous columns as well. Get rid of the Task type and Priority columns by double-clicking them in the Selected box, so that they move back over to Available. Finally, click Save.
Congratulations, you've just created your first custom field on your first custom table in your first custom application. You're catching on quick!
If we wanted to modify the list layout just for us instead of for everyone, we could have clicked the hamburger menu at the top of the content frame, and click Personalize List Columns.
In order to see the configured list view, users will need to click the hamburger menu, go to Personalize List Columns, and then click Reset Columns at the bottom-left of that dialog.