Installing AMPL:
https://ampl.com/try-ampl/download-a-free-demo/
Please follow carefully the instructions corresponding to your operating system.

Working with AMPL with IDE:
1. Create a file "model.txt" with the following text:
var x;
minimize f: x^2;
2. Create a file "script.txt" with the following text:
reset;
model model.txt;
solve;
display x;
3. Save the files "model.txt" and "script.txt" in the folder of your choice.
4. Click on Amplide in your AMPL folder.
5. Open the folder containing the two files.
6. Type "include script.txt" in the console.

Working with AMPL with the terminal:
1. Create a folder called "test" in the AMPL folder.
2. In the test folder, create a file "model.txt" with the following text:
var x;
minimize f: x^2;
2. In the test folder, create a file "script.txt" with the following text:
reset;
option solver './minos';
model test/model.txt;
solve;
display x;
3. Open the terminal and go to the AMPL folder (with the cd command).
4. Type:
./ampl
5. Type:
include test/script.txt;