Citrus trees like a lot of sun, so I would pot it on into a suitable sized pot and move it outside. However, you will need to move it back indoors to a sunny position for the winter as the frost will kill it.

Water it freely during the summer and it will need regular feeding with a high nitrogen feed. An ideal feed for this is liquid lawn food.

Don't feed it in the winter (October to late March) and allow the surface to almost dry out between watering, then water it thoroughly with tepid rainwater.

They need a lot of humidity, so when it's indoors during the winter months stand the pot on a large saucer filled with gravel to create the humidity to the leaves. You could also mist the leaves now and again.

It probably won't bear fruit as commercially produced citrus trees are grafted, but you never know. Even if it doesn't produce fruit, they are evergreen and they make a nice houseplant or garden feature. Pick one of the leaves, crush it and smell it. The lemon aroma is lovely and you can use the leaves for cooking.

thanks for the advice Myron.