You did a good job playing Twinkle by ear. 

I use an iPad or iPhone. Sometimes I lay them flat beside me. I also have a stand that a daughter bought me that I can clip to the table for my iPhone, I also have a stand that I can place my iPad in that stands on the floor. I use that next to my music stand when the sheet music is on MusicScore (I think that is the name of the app - purchased, not free) or it is a PDF that I did not print. I prefer printed out and on a music stand. It is easier to mark up. 

Use what you have in a way that best helps you. 

You should investigate videos on holding the bow and bowing before bad habits cement themselves in your arm and fingers. I noticed issues that will haunt you as you progress and that are causing you to angle bow and bow over the fingerboard. They can be and should be fixed before you get into it too much. Ask me how I know 😁?

I would not go back and forth between resources. For me, it is too confusing. Been there done that. I was constantly changing how I did things, counterproductive. But, it may not bother you. Pay attention as to whether it does help or not, if you use multiple sources for your main learning source. Make sure the two sources work together.

Check out the resource library I started in the cello section a few years ago.

Cello Lesson Links Index

That may have a method of explaining and demonstrating that works for you. I stopped adding to the reference library because there is plenty to get a new cellist going and too much can be too confusing. If nothing there is what suits you, check YouTube.  There are a lot of cello lessons. I can't sit and watch a YouTube video. I use books, but I get the feeling most use YouTube. 

🐭