You have a problem with English.
You clearly do not mean to "check" AT commands - do you mean you need to send AT commands from the Arduino to the ESP8266 and receive the replies in the Arduino?
The compiling problem is that the serial port that you use for programming, is the same one that you need to communicate with the ESP8266. You must disconnect the programming interface to communicate with the ESP8266. A UNO is the wrong Arduino to do this as the connections are fixed internally. You need to use a Pro Mini where is is easier to exchange the connections. You will need to connect "TX" of one to "RX" of the other and vice versa.