This is the camera I used. It's a cheap 3.1 mega pixel Kodak that no one have used the last year.

In the stone age (30 years ago) you bought  special IR film and  a filter that blocked the visible light.  The CCD sensors in a digital camera are already catching infrared light together with the visible light. That isn't so good for the quality of normal pictures, as normal light and IR light doesn't focus at the same distance from the lens it will give unsharp pictures, the color can also be affected. To solve that problem they put a filter in front of the CCD. So the first step is to remove the filter that blocks IR. To do that you need to  take the camera apart, remove the lens and then remove the filter. I couldn't find any description how this camera was put together , so it was to be patient and try to figure out how to get it apart the right way.

Now it is to replace the filter with one that blocks visible light and let the IR light trough. There are expensive filters to buy, but I went for the cheap (free) way, the end of  negative color film often has one or two frames that are developed but has no picture on them (dark in color), they will work as a visible light filter, but won't block IR.  You will need to put two of them on top of each other to get the desired filter effect. You can cut and put them where the old filter sat, but it seemed to be hard to do, so I put them in front inside the protection glass.

The only problem I really had was that the focus had changed ( this is a fixed focus camera, won't be a problem with a manual or auto focus one ), I had to put a little screw and glue a nut on the inside of the plastic tube that holds the lens, so I could adjust the focus when I had put the camera together again. ( The adjust screw  is behind the filter on the pic.

This is the cheap Point And Shot camera I used. You can see the dark "film IR Filter" in front of the lens.

The little piece of glass is the removed filter, leaning on the new filter material.

If you Google the Internet there is a lot of information and ideas how to convert cameras, there are several  who offer to do it for you too.