Below is a guide for installing the FSMC build for Kodi. This is a 3rd party build so please do not post questions on the official Kodi forums relating to this build.
How to Install FSMC Build for Kodi
Open Kodi
Select Settings (cog icon top left)
Select File Manager
Select Add Source
Select None
Type the following EXACTLY https://unhingedthemes.github.io and select OK
Highlight the box underneath marked Enter a name for this media source
Type un then click OK
Go back to your Home Screen
Select Add-ons from the left hand menu
Select Browser (icon that looks like a box top left)
Select Install from zip file
Select un
Select repository.chainsrepo-x.x.x.zip
Wait for the Add-on enabled notification
Select Install from Repository
Select Chains Repository
Select Program add-ons
Select Chains Build Wizard
Select Install
Wait for Add-on installed notification
You will now see a popup regarding settings. You can select any you wish to save and then click continue.
Now select Close in the next window
You should get a message saying there is no build installed. Select Yes
Scroll down and select FSMC Version x.x
Select Continue
The build will now download and install
Click OK when finished and that will force close Kodi
Open Kodi and leave for a couple of minutes so any updates can be completed