HiI have recently moved house and for the first time I have a garden so this is all very new to me

Difficult to advise without more information. How did you prepare the ground before you planted it? What position did you plant it in? Was it in a pot when you bought it, and if so what size pot? Did you give it plenty of water after planting? Water it now in any case.
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This is a deciduous shrub (it will lose its leaves in autumn/winter), so it's quite normal for the leaves to begin to yellow at this time of year. But I wouldn't expect *all* the leaves to have yellowed this early, so there may be something amiss. Could you perhaps provide a photo?

If you've never had a garden before, the most likely explanation is lack of water. Even people who've had a garden a while often get this wrong. The basic principles are these - if you plant something at any time other than in late October, it needs watering, and in the case of a shrub or a tree, it needs significant amounts of water. Not a quick slosh every day either, what they need is a good soak about once a week, so something like a sprinkler left running for a minimum of 20 minutes, or a hose left at the base of the plant trickling gently for 20 minutes. Or a couple of 5 litre cans of water once a week applied to the soil around the base of the plant.

You water in this manner for two reasons - frequent, light watering does not ensure that the rootball of the plant below the soil actually gets any water, and watering in this manner, if the plant survives, encourages roots to head upwards, where they'll sit and wait for you to come along with your can or spray hose every day. If you do it less often (roughly weekly, maybe 5 days if its hot and dry) but copiously when you do water, the water should penetrate down to the rootball and then beyond, into the soil beneath, encouraging deeper rooting, which will mean, after the first year or two, you don't need to water at all unless we're in drought for 3 months.

This advice is applicable for permanent planting, in particular, shrubs and trees - temporary planting such as summer bedding needs watering more often and you needn't be worried about long term effects.

If you've not watered your plant in the manner described, leave the hose trickling at the base for half an hour now. If you're not sure, dig it up, carefully, and inspect the rootball to see whether its dry or not. It's only been in a month, it won't harm it.

sorry - website crashed and it posted the answer again

same again...

Thanks for the kind advice. I am attatching a photo. Sorry its not very clear. The plant was bought for me by my Mom from a mail order site, it was in a pot about 3" wide x 4" deep.

Erm, there is no photo...

I think you can only attach a photo to the first post.

What you can do is click on your own avatar and go to your news page. Click on Questions and select this one. Then click on the option to edit question. There you will see an option to add a photo.