AEM Forms 6.1
FP1 introduces these new features: https://helpx.adobe.com/content/help/en/aem-forms/6-1/whats-new-fp1.html
to upgrade to FP1 - the installation instructions applicable to your environment can be found here : https://helpx.adobe.com/aem-forms/6-1/upgrade.html
in some cases you can directly install the whole feature pack, in other cases it will be a series of small fixes that you will have to install.
FP2 2 simply brings in Japanese language support, and includes all other features from FP1, so you could directly choose to install FP2 as well.
Installation instructions here ::https://helpx.adobe.com/aem-forms/6-1/upgrade.html
The Service Pack 1 is a cumulative fix pack - although my guess is that FP2 would already include the most recent available fixes, but if you want to install SP1, it is delivered as an OSGi package, instead of an installer.
You can either navigate to the CRX console from your AEM Environment and select package share from there, or use the below link to login to package share and download the package which is applicable to your environment.
https://www.adobeaemcloud.com/content/packageshare.html
You will need to create a free Adobe ID, if you haven;t already , in order to login to package share.