Gamemaker Help

I dont know if this is the right place to post is but please move it if it isnt my dear mods.

I need for my computer classes to design a game in gamemaker but the point is, i dont know how.

Is there somebody in here who is experienced with gamemaker and can help me creating the following game?:

Design a game called "My Fourth Game" that has the following properties:

-It knows four objects, obj_man, obj_floor, obj_marker_left and obj_marker_right

-These objects are made visible by four sprites; spr_man_right, spr_man_left, spr_floor and spr_marker

-The player uses the arrow keys to let the man jump and move to the left and to the right

-In the middle of a room is a "river". The man must jump over the river

-Every successful jump gives a point

-Use markers to register a successful jump

image:

So if theres anybody who can help me with this marker stuff that would be great!