It’s a difficult question and you strategy will depend very much on your business, industry and customer base.
Whilst Wordpress can offer SEO tools like Yoast I personally believe that they are somewhat useless if you don’t understand SEO yourself. In a way they provide a false sense of security. After all Yoast is simply a tool to optimise your website with a bit of handholding, they point you in the right direction but it is still down to you. You can have all the SEO tools in the world and still not rank on Google
I would start by researching current SEO trends and how to implement them into an an SEO strategy and in Squarespace. Who and what do you want to target.
Next familiarise yourself with the Squarespace platform. What goes where, where to put page descriptions, how URL are formatted... There are some oddities like image captions but once you’ve gotten used to it you will quickly realise that you can optimise almost all the same things that you can on Wordpress.
Also remember that your websites speed is also a contributing factor to you search engine position. Try to stick to one font, compress your image and try not to use too many scripts.
I have personally managed to get a few websites to rank in the number one spot on Google and they were all hilt on Squarespace so there’s really no reason why you can’t as well. Good luck!