Lenovo ThinkPad T520 User Manual page 152

5. Put the memory slot cover back in place (1), close the cover (2), and then tighten the two screws (3).
6. Reinstall the battery. For details, refer to the instructions in "Replacing the battery" on page 119.
7. Turn the computer over again. Connect the ac power adapter and cables to the computer; then turn it on.
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