Dear Brother/Sister,

Assalam alaikum wa rahmatullah.

The answer to your question is as follows:

As a believer you should try to show others the beauty of religion and its dimensions in order to motivate them into learning about religion and to have a positive inclination towards it. For example, you can demonstrate the teachings of religion and religious values by the way you live and how you apply it to your day to day life, and by doing so your friend will come to realise to what extent the role of religion has in uplifting a person in all aspects of life. Religion exists in our hearts and it has a very strong effect on the way we perceive things, whether it be in our material and spiritual lives or our relations with our family and friends, and so on.

Another thing you can do is when there is an occasion like their birthday or something similar to that you can give your friend a useful and interesting book as a gift or you can invite him or her to attend an informative lecture in the religious congregation you go to.

In any circumstance, all Muslims must strive to invite and show others the religion of Islam, not only by way of tongue, but by actions, behaviour and morals, as a known tradition says: Propagate to people without your tongues (speaking).[i] 

With prayers for your success and apologies for the delay

Thank you,
Wassalam