Hi,
Firstly you’ll need to order a new battery.
While you’re waiting for the battery to arrive, you can do a ***web search*** for ***''“Vivo s1 battery replacement”''*** and familiarise yourself with the process, so you are ready to do the job when you have the parts.
There currently is no Vivo battery replacement guide on iFixit, but you could create one while you’re doing the replacement, to help others out.
Hope this helps