Here's what the Android programmer says about that: to help add the DLC you can download an external file management app like Amaze File Manager (play.google.com/store/apps/details?id=com.amaze.filemanager) or to connect your phone to a computer to move/update the files.
You'll need to redownload and install the base game and any other DLCs you own to have them be up-to-date as well. I'm sorry for the trouble!
I have a samsung s10, so ymmv. Hopefully, this helps (I know there are a lot of steps, but it took me less than 5 minutes):
1. Download the base game from itch.io (this is an .apk file)
2. Download the DLC(s) you purchased (these are .rpa files)
4. Download and install Amaze File Manager from the Play Store
5. Install the base game by clicking on the .apk file and following the prompts to install
6. Open the Amaze app and follow the prompts to allow access to your files, as well as grant "All files access" (clicking Grant will take you to the Settings location, but you'll have to find Amaze in the list, click on its name, and toggle "Allow access to all files" on)
7. Once that setting is toggled on, go back to Amaze and find your Downloads folder there. Inside should be all your .rpa files.
8. Long press on the first .rpa file you want to install and then click on the rest. All of them should be highlighted before the next step.
9. Once highlighted, click on the copy button (an icon of two rectangles in front of each other) at the top of the app
10. Navigate to your Android folder within the Amaze app, then the data folder inside of it. You might have to allow another access prompt here.
11. Scroll down to the "ourlife.demo.apk" file and click on it, then the "files" file inside.
12. At the top of the app, there should be a new folder button (picture of a folder with a +). Click that and make a new folder called "game".
13. Click on the "game" folder, and then click the "Use This Folder" button at the bottom of the app. You will again need to grant access through a prompt.
14. Finally, click the "Paste" button at the bottom of the app, and you should be all set! Open the Our Life app, and enjoy getting married to the best crybaby!!!
