I don't have a lot of information to go on so I'm going to make the following assumptions:
1. These people are older than you
2. They are Conservative Protestant Christians
3. You are trying to inform and convince them of evolution without pissing anyone off
I don't know how you relate to them so here are some tips
There are a few things that are automatic turnoffs to Protestant Christians with regards to evolution. Charles Darwin will shut down any conversation, they are trained to oppose Darwinism as anti-theist propaganda. Another common pitfall is, when you mention evolution, they might interpret it as a replacement for God. After all, if evolution made everything then why would you need to believe in a God? Whether you believe this or not, don't make it the hill you die on. Maybe argue evolution more as a, "God used evolution as a tool to create man." Some Christians argue that one day in the creation narrative is equal to one-thousand years in current day.
Here is an article with a little more detail.
As for explaining evolution
itself, I would use basic examples to support your argument. Everyone kind of gets evolution conceptually. Just try to iron out the kinks and combat the misinformed opinions they likely hold. Point out that humans have adapted different features due to their climate. Different creatures, such as the
peppered moth, have a likelihood of survival proportional to the effectiveness of their color camouflage. What this example shows is that natural selection has caused this species to adapt a particular "camouflage" color. There are
extra bones in certain whale species that are holdovers from their ancestor species. Geologically, you can determine the age of the earth by analyzing layers of sediment,
like we do at the Grand Canyon. If you make a fucky wucky and discuss the age of the earth or the universe,
red shift can be used to help determine the age of the universe and that we are expanding outwards.
A word of warning if they're fundamentalists: They may have read some fundi literature that defends young earth creationism. An example of that is Ken Ham, and that's a whole ordeal of crazy. If that's the case then you need to prepare to debunk this kind of stuff:
Grand Canyon -
Peppered Moth -
Whale Bones -
Red Shift
good luck my dude