Linking Maps // Exporting Maps

Hey there. I hope someone can answer my questions as I have no idea what I'm doing.

I've created two maps and I would like to link them to one but I'm unsure of how to do this. Another issue directly related to this that I'm running into is how do I set the spawn location when you first spawn into a map?

Second issue is I would very much like to make these maps publicly accessible to whoever wants them. How would I go about doing so?

Thanks in advance for any help anyone can give