It is not too hard to host a html5 game in WordPress.
The first thing that you need to do in your wp-admin page is go to the install plugins page, and search for file manager. the link to the plugin on wordpress.org is here: https://wordpress.org/plugins/wp-file-manager/. Install and activate that plugin.
Once you have that installed, you will see the file manager icon on the left menu in the wordpress admin page. Open that page, and you will see a lot of files that are all wordpress files, so do not change them unless you need to.
Right click in the file manager and create a folder. This is the folder we will put the game in. Now open that folder, and all the files for your game into that folder.
Once everything is uploaded, you can right click on the .html file and press get link. Click on the link it gives you, and that is the page with your game in it. That’s all!