Open your Minecraft Launcher, go to "Installations," create a new 1.8.1 profile, and look for the "Server" download link next to the version selection.
Official Mojang links often auto-update to the latest version. To get the specific 1.8.1 version: skachat server maina 1 8 1
You can customize your world by editing the server.properties file with a text editor: Open your Minecraft Launcher, go to "Installations," create