Here are the care instructions that Brooks packages with the saddle:

"...If you follow these simple instructions your saddle will adapt itself to you and retain its support and comfort. A new saddle should be treated with Proofide to help assist the 'breaking-in' process.
Proofide helps keep the leather supple as it is specially formulated from natural ingredients to condition, preserve and showerproof your saddle. Proofide is the only substance that should be used to care for your saddle.
Apply a little Proofide to the finished side of the leather. Allow the Proofide to permeate until dry and then polish off. Proofide should be used several times during the 'breaking-in' period and every 3-6 months thereafter. (On bicycles not fitted with mudguards, an intiial application to the underside of the saddle will be beneficial, this need not be polished off).
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You should protect your leather saddle from moisture. If a wet saddle is ridden the colour may stain your clothing. Allow wet saddles to dry naturally. Never tenion or Proofide a wet saddle.
Correct leather tension will ensure our saddle retains its shape and comfort. A special spanner is availale for this. To tension turn the nose bolt nut 90 degrees at a time, check tension. Over-tensioning a saddle will overstretch the leather fibres and may destroy their structure. Little and not very often is the key. Remember, once the end of the nose bolt is reached, the saddle can no longer be tensioned.
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Your Brooks saddle is guaranteed for two years from the date of purchase against defects in manufacture or materials. If you believe you have a claim under this guarantee, you should retrun the saddle to the place of purchase along with your proof of purchase."