Truly's Sales Process Optimization package is currently listed on the AppExchange. Since this was recently listed and we are still working with the Salesforce team to eliminate dependencies, you have to install the Truly Settings Package before installing the SPO package on the AppExchange.
Installation:
When installing Truly, you should always select “Install for All Users” (the middle of the three options) in order to ensure that it
Sandbox:
We always recommend installing in the Sandbox first. The AppExchange gives you the option to select this as your installation target during the install process.