If File Manager app is complete, you can use this tool (AirMore) to help you install it on your HTC.
1. install this tool on your phone and visit airmore.net to connect your phone with PC by scan the QR code.
2. Once connected, go to "Apps" and click “Install” button to install file manager app.
I installed Astro File Manager app. but failed to figure out how to use it .
What I want to use it for is to rename my photos or videos to a 'meaningful' file name
I hope I can get a step-by-step guide here.
Thanks for your help in advance.

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