The weights provided with IPUMS data give the number of people in the national population represented the single respondent. So, a respondent with a weight of 5.00 represents 5 people in the national population and in a frequency distribution this respondent would be counted 5 times. Most statistical software packages have built in commands for applying weights in analyses and I would recommend looking into the documentation of your statistical program for more details on how to apply these weights.
I hope this helps.