How let cmake know that dependencies must firstly be from a certain location

Usage
3

Also it’s more helpful to users in the future that you just paste the code that is causing you problems instead of linking to the GitHub.

Something like this would suffice:

cmake_minimum_required(VERSION 3.13 FATAL_ERROR)

project(olive-editor VERSION 0.2.0 LANGUAGES CXX)

...

find_package(OpenGL REQUIRED)

find_package(OpenColorIO 2.0.0 REQUIRED)

find_package(OpenImageIO 2.1.12 REQUIRED)

find_package(OpenEXR REQUIRED)

find_package(Qt5 5.6 REQUIRED
  COMPONENTS
  Core
  Gui
  Widgets
  Multimedia
  OpenGL
  Svg
  LinguistTools
  Concurrent
)

find_package(FFMPEG 3.0 REQUIRED
  COMPONENTS
  avutil
  avcodec
  avformat
  avfilter
  swscale
  swresample
)

find_package(OpenTimelineIO)