We all started our journeys with varying backgrounds and experience. I commend you on starting your journey.
There is a basic flow of process that might not be as intuitive from the onset, but is a general place to start with any plasma cutting cnc.
The first - there is a program side of the house. A lot of detail on which image creation and modification software exists like Autocad, Vetric, or Inskape. There are many others out there, free and cost that can be utilized. Some of these will be cloud based or local computer based. My preference is local computer based but there will be hardware requirements like RAM that need to be considered. Big drawings need big horsepower for the drawing editor that you choose. It is a balance and what works for some may not work for everybody. Good detail int he forum to be had for helping make the choice.
There will be a learning curve no matter what, so pick one that works for you. The output of this will be either DXF or SVG for taking the drawing to the next step.
Next step is a post processor - This converts the DXF or SVG to the G-Code that will run on the CNC. Again this is a choice for what works for some, may be different for others. Two choices in the grand scheme of things. Fusion 360 or Sheetcam. Fusion 360 has the added bonus of being incorporated with the Autocad side of the house, so you can have the drawing editor and post processor all in one, but again it will be a large learning curve.
Sheetcam takes either the DXF or SVG file and generates the G-Code necessary for the CNC operating program. It is a stand alone and separate program that resides on the local computer to work best.
Fileshare is a great place to get DXF, SVG or G-Code of the shared files from other users. Use at own risk to make sure the settings are as you need them as you go through the processes.
The final step will be the CNC control program Firecontrol. This what takes the G-Code generated from Sheetcam or Fusion360 and runs the system in the coordinated steps and movements to create the object to be cut.
All of the programs mentioned are available for download to be installed on your local computer. Once installed, you can manipulate the drawing, code or settings to match your setup.
Once they are installed - you get a image, dxf, svg from wherever (online or off) and import to the drawing editor/creator and make any adjustments (size, nodes, details) that are required for your project.
Save as either DXF or SVG on your local computer hard drive.
If working in Fusion360, the next step would be to process within that program for the post processing for the g-code creation. This would be feeds and speeds and height settings to match your material and set up of the cnc machine.
If in sheetcam, the file you created in the Cad program will be imported, and the process within that program for the post processing for the g-code creation. This would be feeds and speeds and height settings to match your material and set up of the cnc machine.
The output from either program will be the G-Code file, which is saved to the local hard drive.
Once on the hard drive, this file is imported to the Firecontrol software for the CNC. This will load the file, and show the outlines that will be cut on the screen. The settings applied during the post proess will determine how fast, how high and how long the torch fires, travels and where on the material all of that will take place.
With the exception of where you find the source dravings or images, everything can be performed on your local hard drive without internet connection.
The one thing an internet connection is good for, is the periodic updates to the programs that can be applied to keep the software updated. This allows identified bugs to be addressed, the program functioning with existing and sometimes enhanced operations and aligned with any advancement that the designers provide.
Hopefully this gives a little better perspective to the fundamental process and helps to refine your questions. There are other posts on this forum that do a great job in answering the same basic process flow and describe the ins and outs well. I just wanted to take the time and put it into my words in an effort to help.
Please use the magnifying glass at the top to search for additional information. Post when challenged and these are a bunch of great guys who provide tremendous support and help along the way.
Enjoy the journey.