Excellent advice from Mattie. Guitars are not easy to play, they will require practice, but having said that, we all find things difficult at first. Like driving, the first time you try to drive a car the pedal control and gear changes are often awful but improve with time, guitar playing is the same.
The golden rule is "ENJOY IT"m don't make it a chore. You can either promise to practice for a set time each day, (not for me, I don't have the discipline) or do like I do and have a guitar near to where you sit (the computer in my case), pick it up for 5 mins and play about, put it down and come back to it later the same day.
Learn a few chords first, you only need 3 to strum a reasonable sounding tune. I would suggest perhaps D,A,G
Here is an excellent chord finder site.
http://chordfind.com/
To recap what Mattie said, do not buy cheap unheard of brands. They are often made of inferior woods and will go out of tune so often, including when you are playing, that you will think guitar playing is 10 times harder than it is and probably give up very soon.
For an acoustic I can recommend the Yamaha FG700MS. I bought mine here and got good service.
http://www.dolphinmusic.co.uk/?keyword=fg700ms &sa=Go&page=shop%2Fsearch_results&manufacturer _id=0
I can recommend the Ibanez electric guitars too.
Remember "Have fun".
Happy playing