There are lots of books that will help you with ideas and tips about writing. Here are two that I’ve come across and know to be good – I’m sure there are lots of others. I’ve linked to Amazon, but it would be best to go along to your local bookshop – you’ll probably find lots more there.
How To Be A Brilliant Writer – the title says it all! It’s really, really helpful, with lots of ideas to get you started and keep you going. It’s by Jenny Alexander.
Write Your Own Adventure Stories, by Paul Dowswell. I think there are others in this series, but this is the one I happen to have. It’s full of excellent tips – and they don’t just apply to writing adventure stories: it covers essentials such as planning, creating brilliant characters, structure, creating tension, settings – all of which apply to any story.