Did do a search but seems we didn't post any information about how to use overrides in general. There is a topic about css but you know whe should definately cleanup things here or make info more visible.
as the topic is mentioning will try to give some information about using overrides for the eventslist and will keep it basic (html-part).
First of all:
read this Joomla article
it will give you insight in how overrides are used and will make it better to understand how the following works.
at default the eventslist view looks like img1, you can modiy the css but if you to complete alter the view it will be possible by using an override and make that file to look like you want.
and copy it to: templates/protostar/html/com_jem/eventslist/default_events_table.php
to check if the file in the template directory is really overriding the "original" file located in the component folder you could edit the file and check it out.
for example you can add
and when viewing the file you'll see it will output the info, see img2.
editing files can be done by a text editor like notepad+/wordpad/notepad etc....
- event-view will be: templates/protostar/html/com_jem/event/
- module-basic: templates/protostar/html/mod_jem/