You will first need to align your sequences, and then feed the alignment to a program that can generate trees. I am very much out of date in this field and I haven't done anything like that in at least ten years, but back when I used to do it, my workflow was:
- Align the sequences using MAFFT or t-coffee.
- Open the alignment in the Jalview alignment editor/viewer which has options to generate the tree:
then just save the tree in Newick format:
The screenshots were taken using the default alignment provided by JalView itself, and this is the tree I got when I saved as Newick:
$ cat tree