You need to import it in a format supported by LMS. To see this format you can view the online help or even perform an export of any devices currently in there to see the formatting.
The online help has sample xml files similar to:
10.77.202.40
Switch6009
cisco.com
Switch2
1.3.6.1.4.1.9.1.281
0
268438100
public
private
lab
lab
lab
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