Ushi No Tane - Harvest Moon

Hi i am on my year 2 Fall and i planted coffee, bananna , cherry and peach tree.

but they are all 0.5 star

i know you need 9 spaces to plant a tree
Example)
000
000
000

but how do you use ferterlizer ? and how do i make them to 5 star.
Do i have to wait until seed maker?

You fertilize your tree just by placing fertilizer next to it. Just make sure that said fertilizer isn't in a trench, or it will fertilize the trench and not the tree. How much fertilizer the tree gets is based on the fertilizer's placement. For example, if the X's are fertilizers, the 0's are the tree, and _ is ground:
X____
X000_
X000_
_000_
_____
The blue X will only give the tree one point of fertilizer, since it's only touching one part of the tree. The purple X will give the tree two points, since it's touching two of the tree spaces. Finally the red X will give three points, since it's touching three spots on the tree.
Now, to get a crop up to five stars, it needs 256 points. Assuming that points on spots stack, a tree arranged like this:
XXXXX
X000X
X000X
X000X
XXXXX
will get 32 points a day. 256 divided by 32 is 8. So, if you arrange it like that, your crops will be at 5-stars in 8 days. 16 fertilizers cost a lot, but once the tree is at 5-stars, it doesn't need any more fertilizer; it'll be good to go. The crops from the trees will surely make a profit at 5-stars.
Finally, you don't need the seed maker to get it to five stars (though if you want more 5-star trees without the need for fertilizer, you will need the seed maker).
Sorry if this was an information overload. I just wanted to cover the all the bases. Hope this helps!

You don't have to wait until seed maker. You can fertilize them while they're still growing. I think good moment is while they starting to be medium tree or mature tree before they can bear fruits. You can also wait until first fruits then you will be able to see star level each time while harvesting fruits, but I think first option is better.

Trees needs large spaces so I just plant them in row and then fertilize (3 bottles for 1 tree). Like this:

000
000
000
XXX

(X-fertilizer)

Thanks for all the detail information..T.T

it helped me alot. thank you so much

A tree takes a lot of time to grow, so you don't need to use that much fertilizer in one go. I just used 3 at a time, and all my trees produced 5 star quality fruits once they matured.

Like sweetstuff6789 said, just make sure every fertilizer is placed in a single space, not on trenches.