This can be a suprisingly difficult task, especially if you and/or members of your team are bad at communicating. 

There are tons of options on how to create your idea. For begginers, it can feel overwhelming to choose which option to use. We used the MIT APP Inventor, which is good, though it has problems if you connect it to an Apple phone/product.

if you google "app coding software"

Before starting on the actual idea, I highly recomned getting used to whatever website, app, coder, ect your team chose. Once you get used to or at least a basic understanding on how to use that option, the creation of your idea will get at least a little smoother.

The project builder, as a begginer, this was overwhelming and confusing, now, it's annoying. Note: This is a picture of version 10.1 because I clicked on the button to take me to the main screen, and it decided to open this version as well... The MIT App Inventor really needs some work.

You don't need a diploma to code. A popular saying is "The difference between a good and a bad coder is their ability to google", in fact I have no formal training with block coding. All you need to succseed is a great googling ability, the ability to apply basic logic, and the ability to be flexible with your ideas

My diploma

In all honestly, you could start coding right away. I highly recomend taking the time to draft out your teams idea before hand, so you can get at least a basic idea on what you are going to make.

A rough draft of the layout and features of the app.

A rough draft of our ideas for the icon

The rough draft for our task/task list screens, it's surprsingly similar to what we have now compared to our other drafts

Now that you have figured everything out, start coding. Depending on what your team is making, I recomend spending the majority of your time coding, this can take a lot of time, especially when you run into an error, or come across an unexpected problem, don't forget to spend a lot of time testing as well, thorough testing is required. Tip: the MIT APP inventor does not have a feature that allows multiple people to do the project at the same time. To get around this, have one person work on the main version that is going to be saved and used, the "Main branch", and have other people work on different aspects of the code, the "side branches". Once it is time to stop coding, have the "Main branch" download all the files from the "side branches" and save (put in backpack) all the code, or just CTRL-C the screen you want to save. Then, have them take all the code, and implement it to the "Main branch".   

(Possibly) the first "Main branch"

Skipping over the middle part (I have no tips for this part). Congratulations! If you made it to this point, you have finished your thing! You (probably) have a working version of your code! Great job!

Me celebrating with my diploma