Read over it once finished to make sure you have changed all necessary fields. Seriously though, just Google some examples and use those as a template, but use your own words and style. It is a terrible time to be looking for work, so don’t be discouraged as it is going to take some time and effort to get through to anybody. Just keep at it, and get your foot in the door somewhere. Experience of any kind will only help your future prospects. Just avoid giving your labour for free.