Below is a simple substitution cipher. There are a number of online tools that could solve this in seconds. The easy first step, therefore, is to decode the text to it's original.
Bhrp pbwyq phecc bhi swwo uem bieah hrp pwm;
Emo Ayrpfrm Ayrpfrem phecc mi’iy sw tq,
Nywu bhrp oeq bw bhi imorms wn bhi jwyco,
Tvb ji rm rb phecc ti yiuiutiyio-
Ji nij, ji heffq nij, ji temo wn tywbhiyp;
Nwy hi bw-oeq bheb phiop hrp tcwwo jrbh ui
Phecc ti uq tywbhiy; ti hi mi’iy pw krci,
Bhrp oeq phecc simbci hrp awmorbrwm;
Emo simbciuim rm Imscemo mwj-e-tio
Phecc bhrml bhiupickip eaavyp’o bhiq jiyi mwb hiyi,
Emo hwco bhiry uemhwwop ahief jhrcip emq pfielp
Bheb nwvshb jrbh vp vfwm Permb Ayrpfrm’p oeq.
The second step is to figure out the rule by which the cipher's key was made. That may seem broad but there is a very definite order by which each letter was assigned which might seem very obvious once the key is laid out.
My goal is to provide a relatively simple challenge as well as to test how effective this method may be applied as a piece to a larger puzzle.