Sunscreen does not necessarily help you tan faster, but it can help prevent sunburns, which could help with the tanning process. Wearing sunscreen is essential, even when tanning, as it helps protect your skin from damage.
Using a sunscreen with SPF 30 and reapplying as necessary is the best way to get tan. SPF 30 offers enough protection while still allowing enough sun to get through to help your skin tan. Taking breaks and not staying out for too long can also help you tan safely. Your skin can only produce melanin for a certain amount of time each day. By only tanning for a small amount of time each day, you can get darker while helping protect your skin.
Remember that all tanning can potentially cause your skin to age faster and can cause skin damage! UV rays cause skin cancers and melanomas. If you really want to tan, wearing sunscreen is the best way to get sun safely.