Just did this in November as was in Moscow over Christmas.
Apart form the places you’ve been to (which information has already been provided), don’t worry if you’ve been to more places than the maximum of 10 that is allowed, just put 10 and that’s it.
The other pain is the previous passports information. If you put your current and if you can get the info of the previous one, great, if not, don’t fret, just make sure you have the passports cover the times you’ve put for being away.
When you go to give in the form and get the biometrics done at one of their sites, I was surprised at how quick it was. I was only there for about 30 minutes, including waiting time. Just make sure you have all the forms that they require.