Step 1 - Open Data Source Manager

• Launch QGIS
• Open 'Layer -> Data Source Manager'
• or use the shortcut icon in the toolbar

Step 2 - Create New Connection

• On the left side select 'WMS/WMTS'
• Click on 'New' to create new connection

Step 3 - Specify Connection Parameters

For server URL set https://firms.modaps.eosdis.nasa.gov/mapserver/wms/[LAYER_TYPE]/<YOUR_M… where ‘YOUR_MAP_KEY’ is the unique code containing both letters and numbers
* Request a Map Key here: https://firms.modaps.eosdis.nasa.gov/mapserver/wms-info/#firms-mapkey

• For [LAYER_TYPE] select from:
  fires
  time_since_detection_4
  time_since_detection_9
  * view supported layers for each layer type
• To customize symbols for URL enter: https://firms.modaps.eosdis.nasa.gov/mapserver/wms/fires/YOUR_MAP_KEY/?…
• Select both Ignore options as shown in the image below
• *note: symbols, colors and size are optional
• The Web Services page provides additional customization details. 

Step 4 - Select FIRMS Layer

• Click on 'Connect' to get the list of available FIRMS layers
• Choose layer of your interest
• Use PNG for transparent imagery

Step 5 - Customize Color

• Open Layer Properties
• Set 'Symbology' option
• Click on 'Colorize' options which will open color picker menu
• Choose your color and click 'OK'

Step 6 - View Results

• The map will display custom symbology