As already mentioned, you must connect your antfarm with an arena. The arena is a place. connected to the antfarm where ants can not escape from. Ants can walk freely on the arena. That is where you should give them food. It can be made in a variety of ways. I will describe the type I use in the configuration I use. You can make all kind of additional modifications.
The configuration I have chosen is very simple to make. This is why you should try to make it more appealing for the ants. This is why I recommend using more natural materials (stones, wood, mould), as well as planting plants. Of course, all should be made so that the ants can not make their nest anywhere that you do not want. That is why you should fill all holes and clefts. If possible use natural materials, instead plasticeine, silicone, glue or rubber.
What you need to make a plaster arena are plaster, shutter box and decoration (stones, wooden sticks, plants to plant). Make the plaster mixture (this time using more plaster, so that it is denser). Pour the mixture in the box and put the sticks, stones and pot in the plaster, so that they stay firmly in the plaster, when it dries. You should put a longer stick and put a feeding "cup" (you can use all kinds of caps) on its top to simulate aphids and make your ants' life more interesting. As mentioned earlier, if you put a pot, you should cover it with small stones, so that ants do not make their nest in it. You can find instructions on how to connect the arena with the antfarm and how to make it escape-prooved on this site too.