I don't wish to sound trite, but are you sure you should be trying this if you know nothing about it? Shares are a very different thing to ISAs and premium bonds. A well-known saying is 'never put money into shares that you can't afford to lose'. And it's true.
But I suppose you'll ignore me, so...
You need to sign up to an online dealing service, one that is execution only. There's loads. (Personally I use TD Waterhouse and have been very satisfied with them) You'll need to jump through loads of hoops to prove your identity. The dealing itself is trivially simple.
Why not have a look on Amazon for books about the basics of share owning/dealing. Or try the numerous money/investment-oriented websites.
If there was an internet site that told you about forthcoming trends in the market, I'm sure it would be very popular. If only it were that simple, this time next year, I'd be a millionaire. Really, you have to work it out yourself, and trust your own judgement. Even experts can be wrong - and frequently are.