Freespirit is right; 15th July is your earliest show date but you can complete your entry forms before then. Most shows need at least 5 weeks from close of entries so that they can prepare but many are available to enter long before that. I think I entered my first few shows when my puppy was 4 months old - I reasoned that if I entered early I was less likely to chicken out!! It also gave me something to work toward.
Shows on 15th July have closed already. Entries closing this week will be for shows from 3rd August onwards. If you view my posts, I recently gave a list of sites I use to find Schedules - these will give you information about classes and closing dates.
I only started showing in January and have now gone spreadsheet bonkers - I'm looking at entries for shows in September and October (gulp). My breeder assures me that my anorak tendencies will wear off after a few years!!
Good luck