There are many guides, and I'd likely pick one and follow it.
Lubuntu is a distribution of GNU/Linux that I'm involved with, so I'll provide their manual; which has a section in it that maybe helpful
manual.lubuntu.me
The link I provided is for the latest
stable release, ie. 21.10 (the 2021-October release), which is
not a LTS or
long-term-support release, so you'll need to
release-upgrade it middle of next year, then you'll be using the LTS release (ie. 22.04 which gets released in 2022-April).
I use a device I
tag in QA-testing (QA=
Quality Assurance) as
`lenovo thinkpad sl510 (c2d-t6570, 2gb ram, i915)`
which is somewhat like yours in specs. It's been used to test all recent Ubuntu
family products (esp. Lubuntu, but also Xubuntu & others too).
I've also used the device in QA-testing Debian releases too (eg. Debian Buster(10), Bullseye(11); I can't recall if I had it for prior releases.. It actually has installed Lubuntu 20.04 LTS (ie. the
latest LTS release), but also has Xubuntu/Xfce on it too (so I can decide which I'll use when I login).
How to download & install - I'll refer back to the Lubuntu Manual I already provided. Even if you don't use Lubuntu, I'd hope the manual is a guide that would apply to any; but other distributions have their own manual (
some are better than others of course) - so give it a try.
Lubuntu uses LXQt and the Qt5 toolkit; so it'll be best with Qt5 apps. With 2GB I do consider the applications with regards what desktop is best; why my box has Xubuntu installed on it too (it's GTK3 based; so if I want to use GTK3 apps - I can login using Xfce which may give better performance).
Beyond resources - there are always our tastes that influence what's best for us; but with 2GB of RAM I'd really consider the RAM. I have to use the sl510 differently to how I use my primary desktop due to the small RAM it has.
I'm typing this on a 2009 dell desktop; but I don't worry about the libraries/toolkits etc. on this box - as it's got 8GB of RAM; but it's a real consideration when you've got <4GB in my opinion (esp. 3GB or less!). This is complexity that will likely turn you off (sorry), but the same applies in the windows or apple mac world; they just tell you need more RAM (
avoiding the why).