Downloading your OSMAnd~ maps to a computer and installing them to your Android phone from there has several advantages:
- Use cheaper or faster network access. In a case where, for example, there is no wifi available but your computer is connected by wired Ethernet network, downloading the maps to your computer is probably much faster and cheaper than using your mobile data plan. (An alternative is configuring tethering at your computer. USB tethering and Bluetooth tethering would work but wifi tethering can be a challenge to set up since most wifi hardware in notebooks does not support access point mode, and Android might not support ad-hoc mode.)
- Avoid tracking. You avoid being tracked by the OSMAnd~ maps server, which else "will send your device and application specs to an Analytics server upon downloading the list of maps you can download" [source].
So, how to do this?
- Just download the relevant zip archives from the OsmAnd maps index.
- Connect your Android phone and unpack the downloaded zip archives into the osmand folder on the SD card. (Alternatively, use
adb push filename.ext /sdcard/0/osmand/according to these answers).
- Start OsmAnd~. It should read and index the files (which for the first startup will take a bit of time).