Thank you very much! I've already solved the problem, and to help others in the future, I'd like to share the solution here:
1.Enter “su” and password in the terminal
2.Enter "nano ~/.bashrc" in the terminal
3.Add "export PATH=$PATH:/home/z/openCARP/physics/limpet/src" on the last line
4.Save and exit bashrc
5.Enter "source ~/.bashrc" in the terminal
6.Enter "make_dynamic_model.sh my_MBRDR" in the terminal after completing the above steps