Londoner here! One option is to enter the lottery to get tickets for the show courts but you are too late for that.
Day of options:
- Join "The Queue". This is an official ticket line that takes place in a park right outside the entrance. Each day, the first 20 or so people in line are able to buy tickets for the show courts (Centre court and Court number 1), but usually people camp overnight for this. Joining the line in the morning is fine but you will almost certainly not be amongst the first 20 people. People farther back in line will be able to buy tickets to the grounds. Grounds tickets will let you enter any of the outer courts (all courts other than the show courts), and if you go within the first couple of days of the tournament all the outer courts will have matches going on, many with big names.
- Buy day of tickets from people who leave partway through the day. You can get into show courts easily this way.
It's a magical wonderful place, utterly beautiful grounds. I really should prioritize going there again, but SW19 is a long way off for me!