Using Cmd prompt:

Step 1: open cmd prompt

Step 2: type command

copy /b picturename.jpg+filename.txt final.jpg

Step 3: it will show same picture as like before only but file will be hided at back of the picture.

Step 4: now we want to open that same file again. Then open that picture with notepad then it`l show our data at the end of the file.

note: this command will not work on win7,vista.

picture and file be in same directory

using software tool:

Step 1: download the software by clicking this below link.
Camoflauge

Step 2: now install in your computer. It's not a virus it'll not harmful to your computer also.

Step 3: Create a notepad file like this and save as hello.txt

Step 4: now right on the file and open with Camoflauge option

Step 5: do the operations as like below process.

Step 6:attach file with any picture or software.

Step 7: enter your unique password to protect from others.

Step 8: finally resultant file will be like as show in figure.

Step 9: now again we want to retrieve that same file then right click on that file and open with uncamouflage .

Step 9: enter password and extract ur file into ur machine.