truth be told man, its not so easy with what you have. actually, its impossible.

impossible because you cant possibly get the same tone as they do without the same gear. thats life. they're using big ol' tube amps with humbucker equipped guitars... you wont be able to get that chunky full sound with a small solid state and single coils. you may be able to get somewhat in the same ballpark though.

play with the settings on your amp- type "Marshall settings" into google, and you should be able to find your amp and some good settings for it. those will be good starters for you, then tweak each setting until you think it sounds best for you. you can also play around with different pickup selections on your guitar, whether its on the neck pickup (all the way left) or bridge (all the way right) or anywhere in between....

it'll take you awhile, but you should be able to get a tone that you like. just keep in mind that you can only do so much with what you have right now.