Here's what you do:
You download these two apps,
MCPE Addons
Dropbox
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After that, download the world you want to import.
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Then, If it has an option(s)
The options might be:
"Open on Dropbox"
"Open with MCPE Addons"
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Next, You open with dropbox or MCPE Addons. If you are on MCPE Addons, Name your addon and World. If it's a Mod, Name it as the mod. If it is a world. Name it as the name. It's that easy. If you have problems trying to download or import your world into MCPE Addons. Look it up.
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Once you are done editing your world, download your world and there you go! You have the world!
I have been doing this and it worked! Hope you enjoyed! Till then,
PEACE!