Own textures from photographs

Only just begun having a look at Unreal Engine 4. My plan is to make a walking simulator with realism in mind. When it comes to creating textures, say I take a photograph of a rock surface or a wall with my camera, to go from jpg to texture available to use in the Unreal Engine, do I need any additional software, or can I directly import jpgs and create textures / texture packs?

Most textures are made from photographs, but you need to process them first, in a lot of cases you would want to make the texture so that it can be tiled, which means the edges need to line up. There are tools like Substance B2M which can take an image and make it tileable and a bunch of other things.
Otherwise you would need to use a photo editing program like Photoshop to do it by hand.
After that you would need to make sure your texture is a power of 2 resolution (like 512x512) and use either PNG or TGA image formats.

You can simply import the .jpg from youre camera into Ued as Texture. Put that texture in the material editor and plug it in the “diffuse” channel. Then select a “constant” node for roughness and specularity and set those parameters with values e.g. between 0 and 1.
save the material and drag it onto youre static meshes or BSP surfaces. done.

Depending on your model and UVs, tiling may not be neccessary in all cases.
What is much more important : Avoid any shadows or highlights in your photographs. Thats the job of the engine.
The best day for shooting (outdoor) texture photos is a bright, but overcast, day with fairly isotrope lighting.
To avoid highlights, you could use a polarization filter.
It may be necessary to adjust the colors a bit as cameras and redoding situations differ. So best is always use a color card for reference.

Thanks for the tips guys. The photography is the simplest part for me, I hear what you say about shooting for low contrast, no problem there. Also if I shoot raw the white balance can be sorted easily in photoshop if not in the camera to begin with. But I have never done full-on game design, and the last time I did anything similar I was using Worldcraft to make Quake 2 maps. I did make custom textures back then, from scanned photographs of walls, but this was 1998!

I’ll have to tile by hand for now seeing the price of Substance B2M, but thanks for the recommendation. I’m trying to learn with a zero budget project and then time will tell.