There are many programs out there.
Like GIMP, which is Photoshop but FREE.
Then there is actually PHOTOHSHOP.
And Personally, many anime artsits like to use Paint Tool Sai.
If your tablets being all funny, check its settings, if all the drivers are installed and the manual.
If that doesn't work, then maybe your hand is quite shaky, and you just need to do some doodling to get used to it.