For video editing (which is what you want to join images and export as video) You can use different programs.
If you want something free (libre) i can reccommend Blender 3D. You can download it for any Operating System.
Now don’t worry Blender is a 3d modeling package that also comes bundled with a video editor among other things.
You can isntall it or download the Zip files to make it portable.
After downloading, simply enter the program, and in the main screen that you will get, press CTRL + Left Arrow and it will change “workspaces” until you find one that is labeled as “Video Editing” in a top left prompt.
Now in the lower part atop the timeline look for a menu that says “Add” > Image , then press Enter / Return in your keyboard.
You’ll get a window overlay that will allow you to locate your image sequence.
Select all the images. To select them properly you need to either sfhit + click on everyone or click, hold and drag a selection box from an empty space (without a file under your cursor) and you’ll be able to select more files at a time.
Now on the left side, there is a panel that is labeled as “Add Image Strip” you need to define the starting frame and the end frame of your image sequence, dont worry though if you have say 100 images, you just leave the start frame at 1 and the end frame at 100.
Then press the button at the top right side called “Add Image Strip”
After you’ve done this you will see a colored bar with the name of your image files inside whats called the graph editor (it’s the one with horizontal grey stripes).
If you click and drag over the graph editor you can see a preview of your animation in the top right black screen.
Now, in order to make it run at 15 frames per second you need to go back to the first screen you saw when opening blender. Press CTRL + Right Arrow to go back to the “Default” layout.
On the right side youll see a bunch of button, look for the tab called “Dimensions”, and you will see a “fram rate” drop down menu. Pick custom and where it says 24 enter 15.
Now go down and find the output tab, and in the first prompt press the folder icon and locate a file folder you would like to use to save your animation.
Press Enter once you’ve selected a folder and accept the selection, similar to when you imported the strip.
Now you will see a drop down menu below the output path, it should say PNG or something else. Press it and select AVI JPEG, dont worry it means that your avi will be compressed. (Tip: if you want to upload it to youtube i reccommend H264 enconding)
On the left side of the file type press RGB for having color or BW fr getting grayscaled video according to the contents of your animation.
You’re almost there! now scroll up until you find the animation button with a clapperboard. Hit it and wait for your animation to render, and that’s it!
If your animation is not at the right speed all you have to do is change the FPS until you get it how you want it.
Hope this was useful, let us know.