false colour IR imagery with digital cameras requires an IR filter which blocks out most but not all of visible light so that there are sufficient data to work with in the green and blue channels of the image.
if one uses too strong an IR filter (eg. 840nm / Wratten 87C filter) which blocks out too much visible light then the only data will be in the red channel and you will end up with only a monochrome IR image
most digital cameras have a sensor sensitive to near IR light up to ~1100nm, but also have a special IR-blocking filter in front of the sensor as the IR light would otherwise degrade the image, thus sensitivity ranges are usually:
the usual recommended IR filter for false colour digital IR imagery is a 720nm filter (alternatives are R72 or Wratten 89B)
placing such a filter on a normal digital camera will result in the need for relatively long exposure times as digital cameras have IR blocking filters on their sensors to give sharper imagery (IR light focuses slightly differently to visible light so a sensor receiving both will have less clarity)
in addition, if your camera is a dSLR and you add such a filter to the lens, you will not be able to see much through the viewfinder, nor will the camera autofocus well, and you will need to resort to Live View mode and manual focus. Furthermore a strong IR blocking filter on the sensor may make false colour IR less effective and some may find in this case a deep red filter will work better than an R72.
a much better alternative is to have your camera modified with removal of the IR blocking filter and replacing it with a 720nm filter
this means you can have much shorter exposures, you don't need to buy IR filters for your lenses, the AF will work (it will need to be re-calibrated for dSLR cameras though - mirrorless cameras are not an issue in this regard), and you can compose through the optical viewfinder or the Live View
when taking your photo, check the red channel on the histogram and adjust the exposures to ensure it does not get blown out / over-exposed
ensure you shoot in RAW file mode