there are a few different ways to achieve this.
1) Make an image of the button and make it a sprite at the location you want. Make another 1x1 image and make that a sprite as well. When the mouse is clicked, position the 1x1 sprite at the mouse location, and check if it is touching the button "sprite collision(1,2)" if it returns a 1 then the button has been clicked.
2) requires no media. Simply write the text to the screen. Then if the mouse has been clicked, check if the mouse is over the text:
center text screen width()/2, screen height()/2, "CLICK ME"
do
if mouseclick()=1
if mousex()>286 and mousex()<356 and mousey()>239 and mousey()<256
cls
print "BUTTON HAS BEEN CLICKED!"
else
text 0, 0, "NO BUTTON CLICKED"
endif
endif
loop