Potential portals are small pre portals. When you arrive to the Waste of Time you can enable one potential portal by clicking the timepod.

They are out of reach usually. Maybe you could shoot them with someting.

There is a crossbow next to Momed at Waste of Time.

They are time portals. So, of course you use the clock hands. Combine the clock hands with the crossbow.

Haven't you already learned that the essential substance for time travel is tachyon?

There is a tachyon slime puddle under the timepod. Use the loaded crowssbow in the puddle. Then shoot the potential portal.