Hi!
Here are a few tips for you:
If you have work to do or are just sitting down to relax, sit by their enclosure to make them more comfortable with your presence. You can also give them veggies while talking to them at the same time, which will ultimately lead them to associate your voice with happiness. You can also let them out for floor time and allow them to come up to you as they please. Whenever they come up to you, offer them a treat in return for their curiosity.
Please remember that guinea pigs are prey animals, and no matter how kind we are to them, we are still predators. It is their natural instinct to run and hide, but do not feel defeated when they do. I have had two of my current piglets since October of 2019. They will climb onto my lap and feel comfortable sleeping beside me but dislike being pet. I have learned to respect their personal space in return for their affection.
You have been given a very helpful link above, please do read it.
How large is their enclosure? ☺