New Posts – Setting default custom field values

I have a WP blog that uses custom fields to allow integration with SIMILE Timeline. The custom fields are:
“icon”
“enddate”
“duration”
“visitag”

I’m not a programmer, but can follow directions well, so please bear with me please.

Questions:
1. How can I modify the WP New Post template to show & plug in default values for the above custom fields?
2. For those custom fields, how can I create dropdown lists for existingt/new values, similar to how the custom fields dynamically provide a drop down list as new metatags are entered.

If you’re interested in what I’m trying to accomplish, take a look at my proof of concept WP site at:

https://www.totalbalance.info/

Thx. in advance.