civilization-6
I know in many (possibly all?) previous Civilization games, cities could only grow to a certain size, and usually you wanted to place your cities far enough apart that they'd all be able to grow without overlapping.
How far apart should I place my cities in Civilization 6 to make sure they don't overlap?
City Renaming has been added with the Fall 2016 update:
Open the city details pane (the highlighted page icon on the panel) and click on the city name in the top left corner of the screen
You cannot.
After more playtime trying to find opportunities to demand this, and investigation online, there does not appear to be any way of demanding an AI move it's armies away.
This sounds like it would be under the "Discuss >" category on the Diplomacy screen alongside the other demands (like "stop converting me" and "don't settle near me"), but I have not seen it, nor has anyone that I have been able to find.
Best Answer
If you want exactly zero overlap and maximum space utilization - place them within 6 empty spaces of each other (each city has workable surrounding area of 3 tiles away from City Center).
It is though reasonable quite often to space them 4-5 tiles away from each other as cities don't usually grow that big.
See this answer to a related Civ V question for visual aid.