Why Use Octave?
In order to work on the labs at home, you will need a program similar to MATLAB called Octave (unless you have paid for MATLAB in which case you can stop reading). Octave has all the features you require for the labs, and they are implemented in exactly the same way. The only difference is that Octave is open-source (free) and MATLAB costs more money than we broke college students can afford. So below are a few links to get you setup and going.
I will provide instructions for Windows and macOS users below. If you are using Linux, I trust you can follow documentation well on your own (just google "octave linux install" and there will be plenty of help).
Go to https://ftp.gnu.org/gnu/octave/windows/. An index page should appear with a list of several files.
Click on the link "octave-4.x.y-installer.exe". This will begin downloading the file. There will be numbers in place of x and y in the link. These denote the version. Use whichever version you wish. Just know which you are using when searching the documentation. Also, keep in mind that the newest version may have more undiscovered bugs than the second newest.
Once the download is complete, open it. You may see several prompts asking if you want to allow this program to be run (make changes to your harddrive, from unknown publisher, etc.). Click yes on all of these. You will then see an installer window. Accept all the defaults and accept all the agreements. The installation will take a few minutes so go for a walk or pet a dog/cat or something while you wait.
After installation is complete, the installer will show two checked boxes, one saying to run Octave and the other saying open the readme file. Leave both checked and click the finish button. Octave should open along with a readme file (probably will open in your web browser). The readme is just some documentation you might find interesting or helpful.
Go to http://wiki.octave.org/Octave_for_MacOS_X. Under the secion "Installing a Mac OS X Bundle, click the link which says "download Octave 4.0.3 with graphical user interface".
You should be taken to sourceforge and the desired file should immediately start downloading. Once it has finished downloading (it should appear as a .dmg file) open it and a license agreement will appear. Click "accept".
Another window will open with an orange arrow pointing from the Octave icon to the Applications folder. Click and drag the Octave icon to the applications folder icon. This will prompt Finder to open your applications folder for you to drop Octave into.
From there you can copy the icon to wherever is convenient for you and run the program as you would MATLAB.
Getting Your Bearings
Looking at the Octave window, you will see several tools that should be familiar. In particular, note that there are 3 tabs at the bottom of the prompt (Command Window, Editor, Documentation). The command window works exactly the same as MATLAB's. Similarly, the editor is where you can edit your scripts. The documentation tab is fairly comprehensive so peruse that at your convenience or if you get stuck (Linux users might have to manually install the required files for this. Again, I assume you know how to google these things.).
Almost always you will find that someone has had your question or problem before and has decided to post it on the internet. If you type "octave plot", you will find more resources than any rational person needs on plotting in octave. Searching is an art that will bear much fruit if done properly.
The homepage for Octave, there are two very important buttons here (download and docs) and some syntax examples. The docs button leads to the official documentation for Octave. Anything you need or really even want to know can be found here.
This is the wiki for Octave and provides more links and advanced topics than you need, but if you're interested, well there you go.