Huawei Y520-U03 - Preparing Your Huawei Phone for Use; Install SIM, Battery, and MicroSD Card; Battery Cover Installation; Initial Battery Charging

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Preparing your phone
To insert the SIM card, the battery and a microSD card please
perform the steps shown in the following figures.
Your phone is shipped with the battery part ially charged. It is
recommended that you fully charge the battery before using it
for the first t ime.
When fastening the battery cover, fasten its upper part
first and then press down the lower part unt il completely
fastened.