Alright so im makeing my own personal town and im getting sick of the default dirt on the ground and i saw a pic that someone had changed the dirt on the ground to a more green color and that what i want to do but i have not a clue how

You have to paint the grass in the landscape editor.

Alright thats cool but now im haveing trouble because in some places it wont work at all it like seems to just stop at a right trianle and i dont know why cause i wanted to put some rocky ground in there two at a smaller scale to make it look like a street in the town

I think you've hit a cell border and need to load the adjacent cell.

Also, you can only have a certain number of textures in a cell, so you may have to remove some of the lesser used ones.

When in landscape mod, press the "I" key (eye key). There are 4 quads in one cell. Press the 'B' key to see the cell boundries. (yellow square grid lines).
Never remove the first texture in any quad or you will get a 'black void'.

And always backup your mod before making landscape changes.