Buy dual SIM card holder. On the market there are several types of such devices. It only remains to choose such that you do not need to cut the SIM card. Self-trimming-SIM-card – is a dangerous business, because in the process you can destroy the SIM card at all.
Insert one of your SIM cards single slot dual mount in the same way as in a normal card holder. You may have to remove the stickers or wrappers that some manufacturers of dual holders are used for fixing a SIM card. In another case the holder might have a little metal valve that you want to insert after the SIM card to hold it in place. Then, similarly to insert the second SIM card in a different slot.
Place the dual SIM card holder in the phone, insert one side in the usual place for SIM-cards. Depending on the model holder should be installed either vertically (that means that you place the battery in the upper part of both SIM cards), or horizontally. In the latter case, you need to do the following: insert one side of the holder in the appropriate slot for the SIM card, put the battery on it, and then just put a different SIM card. Dual SIM card will be enclosed with one side of the battery.
Flip your phone face up. Turn on the camera and find the menu folder or the option with name close to "Dual SIM card". It is with high probability may be the "tool" section of your phone. Once you find this option on the selection will show its capabilities - two phone numbers one mobile network operator, or two networks of different operators. Select the one you want to use at the moment. For a while the phone will lose signal during the change of networks, but this is perfectly normal.