suziedd - I see that you are new to the forum and I highly recommend you introduce yourself in introductions. This way you will let others welcome you and everyone can get a sense of who you are, where in the world are you and what cheese are you interested in.
For your question - what cheese are you trying to do? There are several methods of applying B.Linen an they vary according to the type of cheese you want to make. You can use them with a cheese like Camembert to make some slight flavor, aroma and rind improvements, ot you can use them in cheese like Morbier, Port Salut, Epoisses, Muenster, Limburger etc. to give the rind its orange color while giving the cheese interesting flavors and great aroma - if it's the right kind of cheese for it. B. Linen comes in different varieties that can produce different shades or cream, yellow, orange or red. It usually works best when combined with either cheese yeast and / or geotrichum candidum (often referred to on this forum as "geo"). That is because they help de-acidify the rind and prepare the surface for ideal growth of B.Linen.
To get the orange color and washed rind, the standard practice is to make a light brine of 3% salt and the rest water (brine should be made in a sanitized bottle and use clean filtered water. Kosher salt without additives works best). You add to it a pinch of the B.Linen (1/32 of a teaspoon is enough for 4oz or 100ml water). You let it sit in room temperature for the first 12 hours. You can then spray the cheese with it and rub it with a sponge. You don't have to spray and can just do this with the sponge, however you need to pour the wash into some other dish where you can dip the sponge because it cannot dip in the main bottle for cross contamination issues. Once done, store in refrigerator.
Typically you would begin washing cheese when it is about a week old. You would repeat the washing every 2 days in the first week of washing, then go down to once every 3-4 days in the second week, then 1-2 times in the third week and then stop and let it grow. The orange colors would begin appearing somewhere close to the end of the 2nd week in most cases. It's very gradual and not noticeable at first if you have never seen it before. It will continue to intensify after you stopped the washing treatment altogether.
This is a very typical and general description but it's very different from cheese to cheese. You will have to be more specific...