How can I view my MP4 iles on my old ROKU thing?

[Geek-9pm]

I have an older model ROKU dongle with HDMI for my older TV set. Works just fine for Netflix. And Amazon and other stuff.
But I have  some movies from another source that I have legally downloaded and want to view them on the TV using my ROKU.c They are all MP4 videos.

I tried to Google this and the explanation i got really was hard to understand,  the text was longer than Rip Van Winkle's beard.
https://support.roku.com/article/208754908-how-do-i-use-roku-media-player-to-play-my-videos-music-and-photos-

Has anybody here done this? Is there a simple easy way to do it? 

[Salmon Trout]

It just says that if your Roku has a USB port, put your MP4s on a pendrive/memory stick and insert it into the port. The Roku device needs Roku Media Player to be installed.