If you are trying to get more settlers in Going Medieval, you will need to wait for random events in the game.
In these events, settlers will arrive at your settlement in various circumstances, such as escaping bandit raids or just simply showing up.
To get settlers in these events, you will need to choose the option that allows them to enter your village and accept them when they show up.
However, you might want to build up defenses in the bandit raid situation because if you help them, a raid will arrive in two days.
In this case, you can build walls in this situation by clicking the warfare tab on the bottom right of your screen and equip weapons by clicking on them so your villagers can defend themselves.
But, If you are looking for a faster approach to getting more settlers, there isn't any other than events. However, you can get more settlers at the start of a new game by creating your own custom scenario.
That said, by creating a custom scenario, you can get more settlers at the start of the game by increasing the number of settlers as shown below.
Along with getting more settlers, you can also change other options such as starting resources, starting season, and other conditions such as equipment and settler constraints.
For more on Going Medieval, check out How to build underground storage in Going Medieval.