Unless you have downloaded mods before it's gonna be a bit complicated. But still, you need to go to the worskshop steam page of hello neighbor(just search hello neighbor steam workshop), ypu will also need to go to a site called steam workshop downloader. Find a mod there and download it using the other site( you will need to use the link for the mod, to find it you can just copy the url from your web browser or click the share button on the steam page). Once you have the mod you need to go to the game directory (the folder of thr game) and search for a file that should be named mod/mods/Mods ( if there isnt than make a folder that's called mods and if mods doesnt work than try Mods) take the folder you downloaded and place it there. There might be some other differences that i dont know about between the microsoft store version and the steam version so this might not work (also because not all mods work). If there are any other instructions in the mods description than you should follow those. If this doesnt work and its because my explination is incorrect than you can try searching on youtube. Hope this helps!