roblox studio glitch, How do i fix it?

I can't use Lua efficiently now that i closed the thing on the right of the screen, you know, the one that has all that stuff like Baseplate and ServerScriptService. So i closed it and now i can't open it back up. How do i fix this?

As Sublimus commented, you can enable it back by going to the "View" menu and select the "Explorer" menu item. Additionally, you can right click on your toolbar and check the "Explorer" option.

Another useful trick is to check the "View Tools" option of the toolbar. This will add some additional tools to the toolbar to allow you to quickly show/hide some elements of the Studio easily.