OP, as above we really need more information, however I hope you find the following useful:
Beyond the already installed Photos app you have a choice of Lightroom 6 either stand alone life time licence for around £100 or via monthly subscription along with Photoshop for around £9.99 a month ( probably US dollars is cheaper as we get shafted in the UK

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Most editing work can be done in Lightoom. It is also a full photo management software, for catalogue photos and uploading to Flickr or Facebook or whatever. Many many professionals use it and there are hundreds of tutorials on the web.
Photoshop has a steep learning curve, again the professionals choice but for home use rarely used unless you are blending photos or other specialist need.
Dedicated Mac software includes Pixelmator, available from the App Store. Very very good value, does layers and all sorts of other tricks. I use it mainly for removing unwanted objects or people, it works very well with Lightroom.
You also have Capture One Professional which is a RAW editing software like Lightroom. More expensive than Lightroom but many people ( myself included) believe it gives better results.
So basically, plenty choice depending upon your need. You can try Lightroom and Capture One Pro for 30 days free of charge. That's what I did, best of luck with it.