Last time I looked, unless this is an hourly rate job, this is not possible. (Hourly rate is free form) You have three or four fields, each 200 char max.

Can't really do much more than say "I can do this" and draw attention to your reviews if you have any.

For me this is one of the many red flags on this site. If you're very focused then you can make it work, but for common garden jobs, not so much.