How Can I Give My Cat A Tablet?

With great difficulty is probably the succinct answer to this question!  You can buy a syringe type 'tablet giver' from your vets, but this can be scary for the cat, as it sees you advancing with what looks like a huge needle.  
You can place a towel over the cat to wrap up its limbs and stop it kicking.  Next put your hand over the cat's head, so that your thumb and first finger are just behind the cats canine teeth.  Gently, but firmly tip the head back and the mouth should open.  Press the tablet in as far back as possible.  Close it's mouth and then gently rub on the throat to make the cat swallow.  
Do not simply pop the tablet in the mouth and then let go, or the cat will simply spit out the tablet, the swallowing is the important part.  The cat will undoubtedly view this activity as a grave act of feline abuse so a little treat is probably called for after the tablet has been swallowed.