First you have to find a place that does Western Union. There usually can be found at grocery stores, conveince store or some gas stations.
Once you find a location that does WU, then you will have to fill out a form stating who you are sending the money to, who is picking up the money and how much, etc. When you have completed the form you just take it to the casher/ customer service rep or whoever and they will take it from there. Just bear in mind that there is an addition charge for using WU, and that charge depend on how much money you are sending.
Hope that helps.
BPD