you are referring to an app that’s outdated - it was designed originally for thunkable classic, which is not supported anymore. the current version is called thunkable X.
you may want to refer to a similar chart maker i wrote (for thunkable X) using this link:
however note that data is supplied by editing the blocks to enter the data.
to answer your question, you need to provide logic (ie. blocks) to read a google sheet to provide the data.
you might want to read this link (and other links that refer to gviz) to learn how to handle google worksheet in a systematic way.