Hi Roozbeh8564,
I am glad that you would like to use Ninja to play your own flipbooks 
In case if you would like to play a standard flipbook, Unreal is capable of doing so, it could be played without Ninja.
Manuals on the topics:
Ninja is needed when (A) you would like to use velocity data to interpolate between the frames (eg. slow down playspeed), or…
(B) if you would like to utilze the features (eg. color gradients, opacity settings) of NinjaPlay
Good news is, NinjaPlayers could play any kind of flipbook!
Here are the details on how to incorporate / embed Ninja players to your own project:
FluidNinja Manual
https://drive.google.com/file/d/1TkTxd5_F8GkFiSjOJDRf6i161YNM4E2X
/page 5 / Connect Ninja to your project /Include Ninja Flipbooks and Ninja Flipbook player materials to your project
/page 6 / Migrating NinjaPlay
Once done, just open the player material instance, and pick your flipbook as texture input, plus define the number of columns / rows!
Keep up!