That sketch you have will get data from the BME280 (if it is connected correctly) and display how many characters it has received on your PC screen using serial monitor. You start the monitor from the Arduino IDE by selecting Tools then Serial Monitor. Note that at this point you are not seeing temperatures or anything useful like that you're just establishing if anything at all is getting through.
Once that works the next step is sorting out the data into sensible looking numbers for temp etc. Then it will be time to start thinking about connecting the LCD and getting that to display anything. Then you can go for getting the BME280 information displayed on the LCD.
Little simple steps. Don't try to do everything at once or it will get really frustrating.
Steve