The log folder can be accessed in the app via the Settings->Open Log Folder menu item. If you used the installer, you'll also have a link in your start menu folder for the application to open the log folder. You can also access the logs by typing %AppData%\OBS\logs into start/run. Make sure to close OBS before opening your log file.
Then simply paste the contents of your log, and preferrably use the "Code" button option when posting here on the forums. You can also use pastebin.com as well if you wish. Do not use file download sites, as that will make me very unlikely to view it.