Download instrumental songs. Upload them to your Google Drive account.
*Both tools include music, but you may use these sites if you can't find something you like.
With most programs, you can upload a voiceover you record on your phone!
Tip: Number each voiceover you create to match the photo it belongs with.
On iOS, look for the "Voice Memo" built into your phone. After recording each voiceover, share it by emailing it to yourself or uploading to your Drive. (See below.) Android likely has similar apps-just search Google Play.
iPhones create m4a files. If your program requires mp3 files, go to https://online-audio-converter.com/ to convert your m4a file to a mp3. You can upload from Google Drive, too.
WeVideo allows you to add voiceover directly in the project. The Adobe Spark Video app allows you to record voiceover directly in your project. And, you can upload your voiceover to most programs-it's easy if your voiceover is numbered to match your scene!