You have about 12 weeks before the race so that does give you time to gradually build up your mileage. There are lots of half marathon training plans to be found on the internet as well as this site.
Best advice I can give is;
Build up your mileage gradually.
Try not to do all your mileage on tarmac it's a very unforgiving surface, try running on canal towpaths, parkland and other softer ground for some of your runs.
Don't increase mileage and speed at the same time. If you introduce a faster run or longer run than you have done before, have an easy day the following day.
After two or three weeks of increasing mileage have a slightly easier week to allow your body to recover.
Don't do all your runs wearing the same shoes. You are less likely to get injured if you alternate your running shoes.
If you can gradually build up to being able to run 10 miles in training you should be able to complete 13.1 miles on race day.
...and if you have to walk a little in your first half marathon, so what! I stopped to walk several times in my first half marathon!
Tatton Half Marathon should be a good half marathon for a beginner. It is a mostly flat course, nice scenery, with no nasty surprises and is aimed at beginners as well as faster runners.
Best of luck!
