You can use first person, but very sparingly. For my dissertation, I only used first person "I" in my acknowledgements section to thank my lab supervisors, lab supervisor, etc. for their help in the project.
First person should only be used in metadiscourse (aka when a writer refers to themselves or summarizes their work and thinking process)
You could instead say things like "The aim of this study was to investigate..." etc. Definitely aim to write in third person, and use an impassive academic style of writing.