First Ever Map - A simple arena map After you have downloaded it and have a random .bsp file around, go to Steam, right click tf2 and click properties. Once you have gone to the tf2 Properties menu, click Local Files, then click browse local files. Next you need to click the folder labeled as "tf." Once in there click "maps" and drag the map in.
Why not add some screenshots, so people can get an idea of what the map looks like without having to go through the process of downloading it?
You should add in lights so that your map isn't fullbright. On top of making depth perception easier and your map look better in general, it also means it will be eligible for map tests here. Simply place an entity and change it to "light", then shift+drag them to clone them.
This appears to be a result of following UEAKCrash's tutorials. However, by the point that you've made this map in the series, you've only learned how to make a map that literally functions, and you haven't really gotten into trying to figure out what makes a map play well. I would recommend continuing with the series and learning a bit more before publishing your work, as there isn't really much for us to critique beyond just making sure the doors open.