Hi Jackie, welcome to JY. Hope you have found many people on here who are helpful and friendly.
Do you have any idea whereabouts (country, continent) you would like to go, or the duration or type of holiday (city, beach)? When choosing my first trip with JY, I looked for somewhere in Europe (short flight, familiarity with language) and with a duration of 4 - 8 days (I thought it might be lonely, especially in the evenings - in reality, half the group met up for dinner). It was my first holiday alone, so I wanted to start with a small step. It depends on what you're comfortable with, as some people are confident travellers who don't hesitate at flying halfway around the world for 2 weeks.
Look around the forum for any tips/ reviews of holidays and post if you have a question - most people seem happy to say hi even if they are not going on that particular holiday.
Once you've booked, JY will send you the confirmation and itinerary (including some information and tips for the destination) and you can always call to make any changes/ ask questions.
Look for any JY tags at the airport and start chatting! People will naturally start to socialise once the Tour Manager has gathered the group.
I hope you find a holiday that suits!
P.S. I ended up going to Berlin and loved it (think I posted a review on here).