with my old cat i kinda put her between my legs and gently held her mouth open (though it was harder bc i had to wear gloves with the paladia); but if you look down on them because of the angle it's a lot easier. oh also i remember gently scritching and tickling the under of their chin to get them to open up a little and then dropping it on their tongue/down the throat and then rubbing their neck to get them to swallow. just be gentle obviously

you can also try compounding to either chewable or liquid (most vets will let you do this and pick it right up at a pharmacy), which helped out a lot. liquid is easier because you can just droplet a bunch onto their gums and let them lick it off and chewables are good because they'll just chew it up on their own, usually.