If you need funding for your PhD, there are typically two sources: project scholarships and Fundação para a Ciência e Tecnologia (FCT) scholarships.
Project scholarships can usually be found here: https://apply.uc.pt/explore/scholarships . The duration of these scholarships varies between calls and the output/quality of the work done. Tuition fees may or may not be covered by the scholarship, you need to check the public notice. While these scholarships allow you to finance your research/PhD, they typically also require you to contribute to the project objectives.
FCT PhD scholarships have a call every year. The details for 2023 can be found here: https://www.fct.pt/en/concursos/concurso-bolsas-de-doutoramento-2023-linha-de-candidatura-geral . These scholarships are ideal, as they cover the tuition fees and provide funding for the whole PhD. Best of all, they allow you to focus solely on your research. Notwithstanding, they are very competitive, as there are few scholarships available when compared with the number of applications.