Your Macintosh already comes preinstalled with quite a few software packages. However because macOS is targeted for the general audience, scientific software is mostly missing. If you need additional software, please leave me a note.
Central to the installation of third-party software is the Managed Software Centre found in the Applications folder. You can browse what’s available, however it might be easier to just type a few characters of the name of the program package you indend to use.
Important for UNIX software is the MacPorts. You can either use the version which comes with quite a few programs and utilities preinstalled, or use the bare one and install additional items yourself with the port command. For the latter, the full list of all packages can be obtained with the command port installed.