You have multiple problems here.
The first command code ~/.zshrc is meant to open the file .zshrc located inside your home folder /Users/ocwri (~ is an alias of the home folder) with Visual Studio Code (= code).
It failed with the message command not found: code because ZSH (= your terminal) does not know where VSCode is located. You have to edit a variable named PATH to tell it where to look but a bit more friendly way you can do this is to open your home folder from Visual Studio Code directly and look for a file named .zshrc.
If the file .zshrc does not exists, you can create it from VS Code. You will have to make it executable with the command chmod u+x ~/.zshrc.
You should write the export command inside the file .zshrc. You have to remove the < and > characters. It is used to tell you "please replace this value by yours".
You have the same problem with pdc than you have with code. Your terminal does not know where it is located.
To fix this, you should add the following line inside .zshrc after export PLAYDATE_SDK_PATH:
export PATH=$PATH:$PLAYDATE_SDK_PATH/bin
The PATH variable list every folder where ZSH have to look to find commands (separated by :).
About the command $ pdc MyGameSource MyGame.pdx. The dollar sign is not something you have to write. It is a separator displayed in most terminal before the prompt. Your terminal is using % for the same thing (there is no difference, don't worry).
MyGameSource is the name of the folder containing main.lua. In your case, you are already inside the folder containing main.lua so you can use . (= current folder) instead. However I recommend that you create a folder named Source and move your main.lua inside it.
Edit: changes made to the .zshrc file are loaded when you start a new terminal or when you run it:
~/.zshrc