I sometimes think that aubergines are easy to grow, but hard to grow well if you know what I mean. I find the plants easy to raise, but it’s a harder job to get good fruit. At this stage you should have plants ready for planting out (or you could buy them in a garden centre). You can either plant them out in a greenhouse or polytunnel (spacing is 40cm for standard varieties) or grow them in a 20cm pot in good potting compost.
Aubergines like some humidity so you can place some buckets of water between plants so there is some evaporation happening near them. Removing the growing point of the main stem when the plant is about 25cm high will help to encourage the plant to produce fruit on the side shoots. Once you have about 5 good fruits per plant developing, remove excess side shoots and new flowers. Water well and feed every two weeks with a liquid feed (tomato feed or comfrey tea).