If you don't understand something, here is detailed instruction with screenshots:
The game uses DirectX 8.
For current Reshade version here:
D3D8to9 is required to work:
Although, for this game it's better to use "Better Rayman" as substitution of D3D8to9 (it has also numerous fixes and special, brand new configurator):
Install it, and launch BR3_Config, and choose your resolution (supports widescreen) and check Hardware Vertex Processing. Press OK. It fixes graphical glitches in d3d8to9. Now edit d3d8.ini and in field d3d8to9 change 0 to 1 to turn it on. Since now, Reshade works.
For injecting Reshade in Dolphin:
download Ishiruka Dolphin, and install Reshade as OpenGL while having default DX11 renderer set in Dolphin's settings.