Here is the manual installation process, which works for Proteus 8.0 through 8.17 (and later versions).
If you downloaded a custom library folder (common on hobbyist forums): ir2110 library for proteus 8
Compatible with standard CMOS or LSTTL outputs, supporting logic as low as 3.3V3.3 cap V High Speed: Boasts a typical turn-on delay of 120ns120 n s and a turn-off delay of 94ns94 n s How to Install the IR2110 Library in Proteus 8 Here is the manual installation process, which works
If you cannot find it there, check: C:\ProgramData\Labcenter Electronics\Proteus 8 Professional\LIBRARY . Here is the manual installation process