As you can see from the title, I'm going to try and teach you how to mod Mine Craft. So lets get started! (YOU NEED WINRAR, google it and click on the rar lab website. Go with the free version, and click the download that is in your language and meets your OS 64 bit or 32 bit EX: English 64)

--------Getting a Mod-----------
To get a mod, you'll need to know which mod you want and you will need another mod named Forge(Google forge, not YouTube it). And luckily, YouTube is great for that. Just type in something like "Minecraft mod 1.5.2" and click on a review, as they usually have download links.
Once you get the mod, make sure it matches your version. (Usually you can see the version on the MineCraft title.) If you have a mod for 1.3.2, and your MineCraft says 1.5.2, its not going to work.
------ Installing ------
(Windows 7 here) Click the windows circle to bring up the menu, and type "run" in the search bar (Without the ") After that, type in "%appdata%" (Without the ", keep the % !) A folder should pop up. Click ".Minecraft" (No " again) and go into the mods folder. Drag and drop the mod you downloaded earlier, and go back. Click on bin, and then open minecraft.jar with Winrar. Open up Forge with winrar and drag and drop the files from the Forge winrar window into the minecraft.jar winrar window. After that, delete the file named "metainf". You are free to close the winrar windows when done. Open the minecraft launcher, log in, and enjoy! (Do not close the small "hello" box with a loading bar, that is forge loading the mod.)
------NOTES---------
I am not responsible if you break your saves andor your minecraft andor your legs or your anything while modding. This shouldn't happen if you do it correctly. I'm sorry if any of the text is deformed or strange, although it is awkward typing on a DSi website with a laptop. Mods are not perfect, and they may glitch. Report these glitches to the modders, not me. Not all mods are compatible, and i would suggest to back up your save if you haven't done this before. And to the admins on here (DSipaint), if i am doing anything wrong i will gladly correct it. If there is a typo incorrect step, please calmly state your problem in the comments and i will help the best i can. I do not work forown Minecraft or Mojang. I do own a minecraft account however. I also do not own any mods here, nor do i claim to. I'm sorry for the excessive amount of notes, i don't want to get in trouble or cause trouble.