These warrior tomes can be given to a warrior guild-leader in order for your character to be taught that discipline. The disciplines, once learned, are like spells for us melee characters except using the ENDURANCE pool instead of the MANA pool. These disciplines also have varying recharge times during which that disc or any others similar to it can be used.
For example, if you use the Evasive discipline (WAR 52), it will last for about 3 mins, using 10 ENDURANCE per second, and have a recharge time of 7.8 minutes. That means that you may not use "Evasive" again for 4.8 minutes after it wears off, or any other disciplines like it (Defensive, Fortitude, etc). You may, however, use a skill like "Furious" if ENDURANCE permits, but the same applies to that recharge time and the alike disciplines.
Disc's like Bellow are used once (like "disarm"), at a certain END cost (175) when used, and have a recast time that varies (30 sec).
An important thing to remember is that duration disc's (Evasive, Defensive etc) can be cancelled in the middle of their set duration. This will allow you to switch disc's should a problem arise.
Hope this helps.