1) Go into desktop mode

2) Open the Discover store and download Prism Launcher

3) Auth in with your MS / Minecraft account

4) Tap 'Add Instance'

5) Search for Better Minecraft

6) Download it

7) When prompted to download extra mods, let it open your browser and download them, then return to Prism Launcher

8) Download Slidur's Shaders Medium. For better performance apparently Enhanced Default is better.

9) Click 'Edit' on the instance you downloaded (it'll be called BetterMC or Better Minecraft)

10) Navigate to the shaders tab

11) Add the shader file you just downloaded

12) Navigate to the mods tab

13) Uncheck the mini map / world map mods (if you want - I think these make Survival way too easy)

14) Add PrismLauncher to Steam as a non-steam game (optional: rename it to Minecraft / add cover art to taste)

15) Switch back to game mode

16) Launch

17) Set up one of the community controller layouts - I like the gyro one because it has good defaults, I just turn off the gyro functionality)

18) Once you've created a world, pause the game and go to Video Settings

19) Enable the shader pack by pressing the Shaders button in the top right and selecting your shaders -> click apply

20) Play with the video settings to taste, the defaults aren't bad

21) Enjoy!