There are some requirements to continue with the MLS Sync Plugin, and if you do not meet the requirements, you can not proceed with the MLS Sync.
If you want to meet the requirements and the plugin shows that you are not currently meeting it, you need to make sure that your hosting provider has the resources needed for your hosting service.
Once you are sure that there are no restrictions on your hosting resources, then you can change the php settings to the requirements for MLS Sync.
There are many ways to change php settings and they all affect the php.ini file, so you can create a php.ini in your host root dir (public_html) and change it to your liking.
Read this article to know how you can do this: How to change php settings using php.ini file
Also, if your hosting service has given you access to CPanel, so you can do it using CPanel.
take a look at this article to know how to change php ini file using your CPanel : How to change PHP INI values using CPanel