Hello @Ali2023 and a very warm welcome to the Community Forum 
No you do not need to send out invites to individual sitters, of course you can though if you have seen certain sitter/s that you would like to invite to complete your sit.
For reference, you can also add your TrustedHousesitters profile on to your Forum profile by following the attached link, should you wish. This will then enable others to offer you helpful advice and feedback and will also give your listing extra exposure!
If you are unsure how to do this, or if you have any questions at all, do not hesitate to ask, we are all more than happy to help.
Also, remember you can use the spyglass symbol at the top of the page next to the TrustedHousesitters logo and search for any questions that you may have as they have most likely already been answered on here and of course if not then please just ask! 