Phylogentetics lab-questions?

I have to do a phylogenetics lab without help from the instructor. We've been given 5 "samples" and we have to analyze them to determine the numbers of differences and we have to make a phylogenetic tree.

I have no clue how to do this but this is how I'm attempting it:

I am comparing each letter (in order given) and counting the number that are different amino acids (each letter is a particular amino acid). The ones closest together are the ones that are closest in similarity and the ones with a greater number of differences are further apart.

Does this sound accurate or am I supposed to shift the samples to line up the greatest number of similarities and work from that point?  I just want to make sure I don't waste a bunch of time by starting out wrong.

If anyone has any idea if I'm on the right track or not, I'd appreciate it greatly.

Thanks!
Mamamia