Broadly speaking you could take your ester and mix with 10-20 times the volume of water. The ester probably will not dissolve in the water, but that's okay. You then have to add some sodium hydroxide. Since ester hydrolysis is catalysed by base you don't need an excess but it usually convenient to add a reasonable amount, say half a gram for every gram of ester.
This mixture is then refluxed for a few hours, cooled, and neutralised to around pH 7 with HCl (you can follow this with pH paper). The carboxylic acid might precipitate out but if not you may have to extract it with an organic solvent like ether or chloroform.
As Yggdrasil said, the exact details quantities etc. would depend on the actual ester.