Learn the basics of musical notation. If you are going to convert music from treble clef to bass clef, you have to know the basics of how musical notation is displayed. For the express purpose of transposing treble parts onto the bass staff, you don't need to know anything about different notes, copying them across as they appear will suffice. Notes are displayed on either the higher (treble) or lower (bass) clef, either directly on a line, or in a space between lines.
Use a mnemonic to remember the positions of the notes if required. The notes on the five lines of the treble staff are E, G, B, D and F (from bottom to top), which can be remembered as "Every Good Boy Deserves Fudge." The notes on the lines for the bass clef are G, B, D, F and A, which can be remembered as "Good Boys Deserve Fudge Always." Musical notes run from A to G, and they count upward alphabetically on the musical staff. For example, if you want to find F on the treble clef staff, you count up one space from E, and end up in the space between the E and G lines, which is where the F note goes.
Learn about middle C. On a piano, middle C is the C note in the fourth (or middle) octave. This note separates the bass and treble clef notes. On the treble clef, middle C is two spaces underneath the E on the bottom line, which means it would have to be plotted in open space. If the staff continued downward, it would fall on the next line down below E. To show this, it is practice to draw a horizontal "ledger line" through the note, thus indicating the specific position it is in, even though it doesn't actually fall on the five-line staff. On the bass clef, middle C is located on the line above A, the top line. This is done in the same way as before, with a ledger line to show that the note is one line (or two notes) higher than the top line.
Draw two staffs, one above the other, on a piece of paper. Draw a treble clef to the left of the top one, and a bass clef to the left of the bottom one. Draw a dotted line between the two staffs. This line represents middle C, one line above the bass staff and one line below the treble staff. To plot something from a treble clef staff to a bass clef staff, you need to use middle C as a reference.
Practice transposing notes. For example, a G note on the treble clef (the second line up) would be shown on a bass clef as above the five staff lines, resting on the third additional ledger line up. The first ledger line would represent the position of middle C, the second would represent E (the bottom line of the treble clef) and the third would represent G. Use this theory to transpose notes between treble and bass clefs.