How to start the game?

I thought I am not so stupid, but I've downloaded latest version, noticed it weights only 7Mb, and stuck. No maps, no default trains. Nothing. All tutorials I've found is about how to play, assuming, that I have map, train and so on. But I have no clue how to find starter map and train....

OpenBVE doesn't come with default addons. The reason being, OpenBVE isn't, unlike most sims, country-specific, so there's little common ground for a default addon.

You'll find a bunch of links here: https://bveworldwide.forumotion.com/?pid=3

Also, you can simply google for "BVE addon", OpenBVE supports virtually anything for BVE 2 and BVE 4.

That's great, but adding some quickstart downloads will be great too. I've visited the link, you've provided, but a bit confused, what download are better as tutorial.
Any directions or advices?

You mean as in easy to drive? I think the hungarian routes http://www.bveklub.hu/letoltes/ might be a good start, since they come without ATPs and other such.

That's a real puzzle. Downloaded some archives. In one case can not see a cockpit and the others loading with errors, so I can not see anything except cockpit and roadsigns.
Then tried to use openbve.wixsite.com/openbve/chashinai as suggested tutorial, but have no clue how to combine this 4 archives into something, that game will load successfully.

Try this:

1. Installation help
   
2. Route download
   
3. Train Download
   

It will give you an idea how it works.

Ok, it's been a long night. I installed openBVE and downloaded some suggested content into the legacy folder as directed. I click on the openBVE icon on my desktop and the start-up window opens showing the route I installed. I click on the START button in the bottom right corner of the window but it is grayed-out. How do you get this simulator going? I would appreciate any help you can offer.

Gratefully,
Juke.

Select your route and the train you want to start it with.

Only once both have been selected can you click start.

Yes, I tried that several times. I finally installed an older version, at sites.google.com, and it worked fine. Thanks for your help.