Here, ill explain it all even the bits you know.
Taking a screenshot
Go on SerVeR and press F8. If it worked it will say something about sa-mp-000.png SAVED (near the top left part.) Now go to
Documents > GTA San Andreas User Files > SAMP > Screens There should be your pictures. Right now you have found you Screenshots, your raedy to upload them!
Uploading a Screen shot
Click on this link http://tinypic.com/ which will lead you to the part where you upload your Screenshot. Just click on BROWSE and just locate it to where you save you SCREENSHOT. Once you have BROWSE your picture just click UPLOAD NOW!. Once you've finished uploading your picture it will lead you to the URL LINKS that you will need. One will say
IMG Code for Forum & Message Boards Just copy the link under it. Now your done with that page.
Putting it into a forum
Now just paste that link you copyed onto your topic (The bit where you write)
It will be something like this
(NOTE: the i56.tinypic.com etc. will not be the same)
Now, just delete the and make then small characters. E.g
HAHA = haha
Now your ready to go!
JUST HIT SUBMIT!!
I hoped i helped you all and Goodluck!