If you're new to pnpm then you should read the pnpm documentation.
Day to day usage is similar to npm or yarn. The main difference is that pnpm uses a single node_modules folder for all packages.
Consider adding aliases
I recommend adding aliases to your shell to make it easier to run pnpm commands. If you use Miller DevShell you should have these already.
alias pnpm="pnpm"
alias pnr="pnpm run"
alias pui="pnpm update --recursive --interactive"
Common commands
# install dependencies
pnpm install -r
# update dependencies (I personally use `pui` above instead)
pnpm update -r
# run a script (I use `pnr <script>` instead)
pnpm run <script>
# run a script in a specific package
pnpm run <script> --filter='backend'