Ft. Lauderdale, Fl USA
First, when writing in structured form, the syllable counts must be consistent. Here are the syllable counts of your lines..
As you can see, they are not too bad! You went off the road a few times, but overall you did pretty well. You still need to correct the discrepancies, though.
Next you have to choose the meter. Whether you choose iambic, trochaic, anapestic or whatever, you need to have consistency in the lines.
Let's take the first stanza with the accented syllables in caps..
JES-se JAMES and his BRO-ther FRANK
in COLD, stern DAY-light ROBBED a BANK
the LEG-ends SAY they HELPED the POOR
WITH the TREA-sure THEY se-CURED.
The first line starts trochaic (DA-dum), the second iambic (da-DUM), the third iambic and the fourth trochaic. That could be acceptable if all of the other stanzas followed the same format, but they don't.
Many of these glitches can be easily fixed. The first stanza, for example can be made perfect with two small changes that will maintain the meter AND correct the syllable counts.
Young Jesse James and brother Frank
In cold, stern daylight robbed a bank.
The legends say they helped the poor
With all the treasure they secured.
Adding "young" in the first stanza and "all in the last stanza made all the difference. Now you have to go through all of the stanzas, find the glitches and make the corrections. Poetry IS complex and the easier it is to read and the smoother it sounds means the more work went into it to make it that way.
You are on your way, new poet. Welcome.....