Hiding the tablet in something nice often works. You can use soft cat treats with holes in them for example, or some tinned cat food or pate. Soft cheese or peanut butter may work for some cats. Check, if necessary, whether this type of food is suitable for your cat.
If all this fails, you will have to actually push the tablets into your cat's mouth. To do this, you place one hand over the muzzle and gently introduce your thumb and forefinger into the mouth by pushing the lips inwards just behind the canine teeth. You can even try to put some pressure onto the hard palate as this will help to keep the mouth opened. The other hand is then used to further open the mouth by pushing the lower jaw down and putting the tablet as far into the mouth or throat as possible. After closing the mouth, gently stroke the throat to induce swallowing. In some cases it may be advisable to give some water afterwards to help the cat to swallow.
Some tablets can be crushed and put into food. The vet can tell you if this is possible with the tablets supplied. There are special tablet crushers available to this purpose. If you have not got access to these, you can crush a tablet with the back of a spoon for instance.