Place Expanded_Inventory_1.0.1 in your factorio data directory. 

Place the entire folder into the data directory, not just the files inside.

For Steam users, this is loated at C:\Program Files (x86)\Steam\steamapps\common\Factorio\data\
For 64 Bit users, this is located at C:\Program Files (x86)\Factorio\data\
For 32 Bit users, this is located at C:\Program Files\Factorio\data\

This should result in the following file locations:
C:\....\Factorio\data\Expanded_Inventory_1.0.1\data.lua
C:\....\Factorio\data\Expanded_Inventory_1.0.1\info.json
C:\....\Factorio\data\Expanded_Inventory_1.0.1\readme.txt (optional)

By default the inventory is expanded to 100. For 120 and 150 options please edit "data.lua" and comment out the default value by adding '-- ' without the quotes before the second line, and remove these quotes from the line with your ideal setting (120 and 150).