Press the green flag. Then press anywhere except the clouds & then a number 1-100 will be generated in the top right corner. Also for those who don't know RNG means Random Number Generator.
Here's the other RNG games I've made: Random Number Generator 1-10 https://scratch.mit.edu/projects/1119044372/ Random Number Generator 1-1000 scratch.mit.edu/projects/1119040934/